INTERVIEW QUESTIONS PART 3

PHP interview questions, Part 2
Web dev interview questions
1. How can we repair a MySQL table?
2. What are the advantages of stored procedures, triggers, indexes?
3. What is the maximum length of a table name, database name, and fieldname in MySQL?
4. How many values can the SET function of MySQL take?
5. What are the other commands to know the structure of table using MySQL commands except explain command?
6. How many tables will create when we create table, what are they?
7. What is the purpose of the following files having extensions 1) .frm 2) .myd 3) .myi? What do these files contain?
8. What is maximum size of a database in MySQL?
9. Give the syntax of Grant and Revoke commands?
10. Explain Normalization concept?
11. How can we find the number of rows in a table using MySQL?
12. How can we find the number of rows in a result set using PHP?
13. How many ways we can we find the current date using MySQL?
14. What are the advantages and disadvantages of Cascading Style Sheets?
15. What type of inheritance that PHP supports?
16. How can increase the performance of MySQL select query?
17. The structure of table view buyers is as follows:
18. +----------------+-------------+------+-----+---------+----------------+
19. | Field | Type | Null | Key | Default | Extra |
20. +----------------+-------------+------+-----+---------+----------------+
21. | user_pri_id | int(15) | | PRI | NULL | auto_increment |
22. | userid | varchar(10) | YES | | NULL | |
23. +----------------+-------------+------+-----+---------+----------------+
the value of user_pri_id the last row 2345 then What will happen in the following conditions?
Condition1: Delete all the rows and insert another row then. What is the starting value for this auto incremented field user_pri_id ,
Condition2: Delete the last row(having the field value 2345) and insert another row then. What is the value for this auto incremented field user_pri_id
24. What are the advantages/disadvantages of MySQL and PHP?
25. What is the difference between GROUP BY and ORDER BY in Sql?
26. What is the difference between char and varchar data types?
27. What is the functionality of md5 function in PHP?
28. How can I load data from a text file into a table?
29. How can we know the number of days between two given dates using MySQL?
30. How can we know the number of days between two given dates using PHP?
31. How can we change the name of a column of a table?
32. How can we change the name and data type of a column of a table?
33. What are the differences between drop a table and truncate a table?
34. When you want to show some part of a text displayed on an HTML page in red font color, what different possibilities are there to do this? What are the advantages/disadvantages of these methods?
35. When viewing an HTML page in a Browser, the Browser often keeps this page in its cache. What can be possible advantages/disadvantages of page caching? How can you prevent caching of a certain page (please give several alternate solutions)?
36. What are the different methods of passing data or information between two calls of a web page? What are the advantages/disadvantages of these methods?
37. An Apache web server is running on a Linux system. Suddenly, the web server delivers the pages very slow. How could you find out possible reasons for that (when using system commands, please specify their names)?
38. What are the different ways to login to a remote server? Explain the means, advantages and disadvantages?
39. Please give a regular expression (preferably Perl/PREG style), which can be used to identify the URL from within a HTML link tag. Example: The regular expression should match the tag and give the URL (”http://www.yoursite.com /”) as a return result. Tags should also be matched if they contain other attributes than the HREF attribute.
40. A select query over a large table runs very slow because of the growing number of entries in that table. What different measures could be taken to improve speed?
41. A company wants to store their invoices in a database. They already have their customers and articles in that database. Both customer and article are each identified by an unique integer value. Please create the SQL statements for creating the necessary table(s) for storing the invoices in a MySQL database. An invoice should hold information like invoice number, customer, date, article(s) and quantity etc.
42. For the database from the previous question, please give an SQL query which returns the invoice number of all invoices which contain the article with the number “1234″. The query should be able to run under a MySQL 4.0 database.
43. How would you backup and restore a big MySQL database? What are the advantages of the approach which you have taken over the others?
44. Create a PHP web script with the following attributes: on start, three HTML form elements are shown: an string input field, a checkbox field, a dropdown/pull down list with 5 elements and a submit button. On submission, the form should be redisplayed (while remaining all options/inputs as the user has selected/entered them). Additionally, the selections/inputs of the user should be displayed in text. Please solve this without the use of any external libraries.
45. What is MIME?
46. What is PEAR in PHP?
47. How can I use the COM components in PHP?
48. How can I load the DLLs dynamically?
49. How many ways we can give the output to a browser?
50. How can we know that a session is started or not?
51. What is the default session time in PHP and how can I change it?
52. What changes I have to done in PHP.ini file for file uploading?
53. What are the differences between MySQL_fetch_array(), MySQL_fetch_object(), MySQL_fetch_row()?
54. How can I set a cron and how can i execute it in Unix, Linux, and windows?
55. Steps for the payment gateway processing?
56. How many ways I can register the variables into session?
57. Explain different types of errors in PHP (i.e. arguments in errorreporting function)?
58. How many ways I can redirect a PHP page?
59. List out different arguments in PHP header function?
60. What type of headers have to add in the mail function in which file a attached?
61. What is the difference between
62. What are the differences between PHP3 and PHP4 versions?
63. What are the differences between include() and include_once() functions?
64. Describe the importance of DABA BASE ABSTRACTION LAYERS in PHP and database connection?
65. Explain MySQL optimization?
66. What is the difference between using copy() and move() function in PHP file uploading?
67. What is the difference between Reply-to and Return-path in the headers of a mail function?
68. Explain about Type Juggling in PHP?
69. How can I get the only name of the current executing file?
70. How can I embed a java programme in PHP file and what changes have to be done in PHP.ini file?
71. How can I find what type of images that the PHP version supports?
72. The table tbl_sites contains the following data:
73. -----------------------------------------------------
74. Userid sitename country
75. ------------------------------------------------------
76. 1 sureshbabu indian
77. 2 PHPprogrammer andhra
78. 3 PHP.net usa
79. 4 PHPtalk.com germany
80. 5 MySQL.com usa
81. 6 sureshbabu canada
82. 7 PHPbuddy.com pakistan
83. 8. PHPtalk.com austria
84. 9. PHPfreaks.com sourthafrica
85. 10. PHPsupport.net russia
86. 11. sureshbabu australia
87. 12. sureshbabu nepal
88. 13. PHPtalk.com italy
Write a select query that will displayed the duplicated site name and how many times it is duplicated? …
Make sure you read Part 1 of PHP interview questions.

41 Comments so far »
1. Shatabdi said,
1. How can we repair a MySQL table?
The syntex for repairing a mysql table is
REPAIR TABLENAME, [TABLENAME, ], [Quick],[Extended]
This command will repair the table specified
if the quick is given the mysql will do a repair of only the index tree if the extended is given it will create index row by row
2. Shatabdi said,
3. maximum lenghth of mnames of database, table, columns
database- 64
table -64
columns-64
alias-255
3. Shatabdi said,
4.How many values can the SET function of MySQL take?
Mysql set can take zero or more values but at the maximum it can take 64 values
4. Kumar said,
What are the other commands to know the structure of table using MySQL commands except explain command?
describe table_name;
5. Kumar said,
How can we find the number of rows in a table using MySQL?
How can we find the number of rows in a result set using PHP?
Use this for mysql
>SELECT COUNT(*) FROM table_name;
but if u r particular about no of rows with some special result
do this
>SELECT [colms],COUNT(*) FROM table_name [where u put conditions];
and for PHP it cant be more simple
$result = mysql_query($any_valid_sql, $database_link);
$num_rows = mysql_num_rows($result);
echo “$num_rows rows found”;
6. Kumar said,
How many ways we can we find the current date using MySQL?
SELECT CURDATE();
CURRENT_DATE() = CURDATE()
for time use
SELECT CURTIME();
CURRENT_TIME() = CURTIME()
7. Kumar said,
Give the syntax of Grant and Revoke commands?
The generic syntax for grant is as following
> GRANT [rights] on [database/s] TO [username@hostname] IDENTIFIED BY [password]
now rights can be
a) All privilages
b) combination of create, drop, select, insert, update and delete etc.
we can grant rights on all databse by usingh *.* or some specific database by database.* or a specific table by database.table_name
username@hotsname can be either username@localhost, username@hostname and username@%
where hostname is any valid hostname and % represents any name, the *.* any condition
password is simply the password of user
The generic syntax for revoke is as following
> REVOKE [rights] on [database/s] FROM [username@hostname]
now rights can be as explained above
a) All privilages
b) combination of create, drop, select, insert, update and delete etc.
username@hotsname can be either username@localhost, username@hostname and username@%
where hostname is any valid hostname and % represents any name, the *.* any condition
8. Kumar said,
The structure of table view buyers is as follows:
+—————-+————-+——+—–+———+—————-+
| Field | Type | Null | Key | Default | Extra |
+—————-+————-+——+—–+———+—————-+
| user_pri_id | int(15) | | PRI | NULL | auto_increment |
| userid | varchar(10) | YES | | NULL | |
+—————-+————-+——+—–+———+—————-+
the value of user_pri_id the last row 2345 then What will happen in the following conditions?
Condition1: Delete all the rows and insert another row then. What is the starting value for this auto incremented field user_pri_id ,
Condition2: Delete the last row(having the field value 2345) and insert another row then. What is the value for this auto incremented field user_pri_id
In botth cases let the value for auto increment field be n then next row will have value n+1 i.e. 2346
9. Kumar said,
What is the difference between char and varchar data types?
Set char to occupy n bytes and it will take n bytes even if u r storing avalue of n-m butes
Set varchar to occupy n bytes and it will take only the required space and will not use the n bytes
eg. name char(10) will waste 5 bytes if we store ‘kumar’, if each char takes a byte
eg. name varchar(10) will just use 5 bytes if we store ‘kumar’, if each char takes a byte. rest 5 bytes will be free.
10. Kumar said,
What is the functionality of md5 function in PHP?
string md5(string)
Calculate the md5 hash of a string. The hash is a 32-character hexadecimal number. I use it to generate keys which I use to identify users etc. If I add random no techniques to it the md5 generated now will be totally different for the same string I am using.
11. Kumar said,
How can I load data from a text file into a table?
The mysql provides a LOAD DATA INFILE syntax. U can load data from a file. Gr8 tool but u need to make sure that
a) data is delimited
b) u match the colms and data correctly
dont use w/out first learning the syntax
12. Kumar said,
How can we know the number of days between two given dates using MySQL?
Use DATEDIFF()
>SELECT DATEDIFF(NOW(),’1947-08-15′);
will give u the exact no of days India got independence from British.
13. Kumar said,
How can we know the number of days between two given dates using PHP?
Simple arithmetic.
$date1 = date(”Y-m-d”);
$date2 = “1947-08-15″;
$days = (strtotime() - strtotime()) / (60 * 60 * 24);
echo ” No of $days we got independence from Britts”;
14. Kumar said,
How can we change the name of a column of a table?
How can we change the name and data type of a column of a table?
this will change the name of colm
> ALTER TABLE table_name CHANGE old_colm_name new_colm_name
this will change the name of colm and also the datatype
> ALTER TABLE table_name CHANGE old_colm_name new_colm_name [data type]
15. Kumar said,
What are the differences between drop a table and truncate a table?
>DROP TABLE table_name
Will DELETE the table and DATA
>TRUNCATE TABLE table_name
Will DELETE the table DATA not the table definition
16. Jigar said,
The structure of table view buyers is as follows:
+—————-+————-+——+—–+———+—————-+
| Field | Type | Null | Key | Default | Extra |
+—————-+————-+——+—–+———+—————-+
| user_pri_id | int(15) | | PRI | NULL | auto_increment |
| userid | varchar(10) | YES | | NULL | |
+—————-+————-+——+—–+———+—————-+
the value of user_pri_id the last row 2345 then What will happen in the following conditions?
Condition1: Delete all the rows and insert another row then. What is the starting value for this auto incremented field user_pri_id ,
Condition2: Delete the last row(having the field value 2345) and insert another row then. What is the value for this auto incremented field user_pri_id
Mr. Kumar has given its answer but if you have used mysql as backend and if you fire a query “delete from tablename” then in mysql it will reset auto index. so for condition one it will start from value 1.
for condition 2 it will start from n+1
17. Jigar said,
What is PEAR in PHP
PEAR is short for “PHP Extension and Application Repository” and is pronounced just like the fruit. The purpose of PEAR is to provide:
A structured library of open-sourced code for PHP users
A system for code distribution and package maintenance
A standard style for code written in PHP
The PHP Foundation Classes (PFC),
The PHP Extension Community Library (PECL),
A web site, mailing lists and download mirrors to support the PHP/PEAR community
PEAR is a community-driven project with the PEAR Group as the governing body. The project has been founded by Stig S. Bakken in 1999 and quite a lot of people have joined the project since then.
http://pear.php.net/manual/en/introduction.php
18. Nasim Abbas said,
A .66
select count(id) id ,sitename from tbl_sites group by sitename having id>1;
19. Sergej said,
What is the difference between GROUP BY and ORDER BY in Sql?
ORDER BY [col1],[col2],…,[coln]; Tels DBMS according to what columns it should sort the result. If two rows will hawe the same value in col1 it will try to sort them according to col2 and so on.
GROUP BY [col1],[col2],…,[coln]; Tels DBMS to group results with same value of column col1. You can use COUNT(col1), SUM(col1), AVG(col1) with it, if you want to count all items in group, sum all values or view average
20. Sergej said,
39. What is MIME?
MIME is Multipurpose Internet Mail Extensions is an internet standard for the format of e-mail. Howewer browsers also uses MIME standart to transmit files. MIME has a header wich is added to a begining of the data. When browser sees such header it shows the data as it would be a file (for example image)
some mimes:
audio/x-ms-wmp
image/png
aplication/x-shockwave-flash
21. pupu said,
44.How can we know that a session is started or not?
a session starts by session_start()function.
this session_start() is always declared in header portion.it always declares first.then we write session_register().
22. pupu said,
47.What are the differences between MySQL_fetch_array(), MySQL_fetch_object(), MySQL_fetch_row()?
Ans:- MySQL_fetch_array()->Fetch a result row as an associative array,numeric array.
MySQL_fetch_object()->Fetch a result row as an object.
MySQL_fetch_row()->Fetch a result set as an array().
23. Kripa said,
If we login more than one browser window at the same time with same user and after that we close one window then is the session is exist to other window or not.And if yes then why? or if no then why?
24. YQwe said,
If we login more than one browser window at the same time with same user and after that we close one window then is the session is exist to other window or not.And if yes then why? or if no then why?
session depends on browser. if browser is closed then session is lost. the session data will be deleted after session time out. if connection is lost and u recreate connection, then also sesssion will continue in the browser.
25. Abdu Rahiman said,
What is the maximum storage capacity of Mysql data,
Is Mysql not reliable, Why?
26. m. sivakumar said,
What are the database files stored in system?
Ans: data’s are stored in name.Myd
table Structure are name.$frm
Index tables are name.myi
27. m. sivakumar said,
what is the difference between groupby and order by in mysql?
Ans: Group by which is used to sort a table interms of colums
order by which is used to index a table by colum value
28. Moses Dinakran said,
Question No 47.
The difference between mysql_fetch_row() and mysql_fetch_array() is that the first returns the results in a numeric array ($row[0], $row[1] etc), while the latter returns a the results an array containing both numeric and associative keys ($row[”name”], $row[”email”] etc). mysql_fetch_object() returns an object ($row->name, $row->email etc).
29. sivakumar said,
difference between php4 and php5?
php4 cannot support oops concepts and zend engine1 will be used
in php5 support oops concepts and zends engine2 will be used
error supporting will increased in php5
xml and sqllite will be incresed in php5
30. amrita said,
if i have to use more than one forms in more than one function in javascript and use it in a single html page,how should it be done
31. Ashish Mathur said,
A.How can increase the performance of MySQL select query?
We can use LIMIT to stop MySql for further search in table after we have received our required no. of records, also we can use LEFT JOIN or RIGHT JOIN instead of full join in cases we have related data in two or more tables.
32. ALAGARSAMY said,
what about ob_start and ob_flush?
Ans:
ob_start is used to start the output buffer
ob_flush is used to refresh or clear the output buffer
33. Senthil said,
What is difference between MySql 4.0 and Mysql 5.0
34. nilanjan banerjee said,
what the difference between
mysql_connect and mysql_pconnect?
35. alagarsamy said,
father of pms
savan
36. siddhant singh said,
ALL MYSQL QUERY WHICH USED IN PHP.
1. mysql_connect
2. mysql_pconnect
3. mysql_select_db
4. mysql_query
5. mysql_fetch_array
6. mysql_fetch_assocs
7. mysql_fetch_row
8. mysql_fetch_object
9. mysql_close
10. mysql_fetch_field
11. mysql_fetch_leanth
12. mysql_fetch_affected_rows
13. mysql_create_db
14. mysql_data_seek
15. mysql_db_name
16. mysql_db_query
17. mysql_drop_db
18. mysql_error
19. mysql_field_flags
20. mysql_field_len
21. mysql_field_table
22. mysql_field_type
23. mysql_field_seek
24. mysql_free_result
25. mysql_insert_id
26. mysql_first_dbs
27. mysql_list_field
28. mysql_ping
29. mysql_hum_field
30. mysql_read_escape
can anyone tell me is this all complet query. which is used in php.
37. Rakesh Chandel said,
mysql_pconnect() is used to make a persistence connection to a database means that we can not close a persistence connection using mysql_close() also if a connection is already opened mysql_pconnect will use that connection and will not create another connection.
38. PHP interview questions, Part 1 | TechInterviews.com | « Interview questions for tech companies said,
[…] done? Read the second set of interview questions on PHP, or leave comments […]
39. Manokaran said,
What is Normalization ?
The process of simplifying a complex table into a simple form.
40. Manokaran said,
How many can ways we redirect from php page?
i. We can redirect from php page using header() function
ex:
—
header(”location:PAGE_NAME | PAGE_PATH”);
41. Meganathan said,
Different types of error reporting in php ?
error_reporting() function and its constant values
—————————————————
E_ERROR
E_WARNING
E_PARSE
E_NOTICE
E_CORE_ERROR
E_CORE_WARNING
E_COMPILE_ERROR
E_COMPILE_WARNING
E_USER_ERROR
E_USER_WARNING
E_USER_NOTICE
E_ALL
E_STRICT
E_RECOVERABLE_ERROR

INTERVIEW QUESTIONS PART 2

Q:1	What are the differences between Get and post methods in form submitting. give the case where we can use get and we can use post methods?
A:1	When to use GET or POST The HTML 2.0 specification says, in section Form Submission (and the HTML 4.0 specification repeats this with minor stylistic changes): –>If the processing of a form is idempotent (i.e. it has no lasting observable effect on the state of the world), then the form method should be GET. Many database searches have no visible side-effects and make ideal applications of query forms. – –>If the service associated with the processing of a form has side effects (for example, modification of a database or subscription to a service), the method should be POST. How the form data is transmitted? quotation from the HTML 4.0 specification –> If the method is “get” - -, the user agent takes the value of action, appends a ? to it, then appends the form data set, encoded using the application/x-www-form-urlencoded content type. The user agent then traverses the link to this URI. In this scenario, form data are restricted to ASCII codes. –> If the method is “post” –, the user agent conducts an HTTP post transaction using the value of the action attribute and a message created according to the content type specified by the enctype attribute. Quote from CGI FAQ Firstly, the the HTTP protocol specifies differing usages for the two methods. GET requests should always be idempotent on the server. This means that whereas one GET request might (rarely) change some state on the Server, two or more identical requests will have no further effect. This is a theoretical point which is also good advice in practice. If a user hits “reload” on his/her browser, an identical request will be sent to the server, potentially resulting in two identical database or guestbook entries, counter increments, etc. Browsers may reload a GET URL automatically, particularly if cacheing is disabled (as is usually the case with CGI output), but will typically prompt the user before re-submitting a POST request. This means you’re far less likely to get inadvertently-repeated entries from POST. GET is (in theory) the preferred method for idempotent operations, such as querying a database, though it matters little if you’re using a form. There is a further practical constraint that many systems have built-in limits to the length of a GET request they can handle: when the total size of a request (URL+params) approaches or exceeds 1Kb, you are well-advised to use POST in any case. I would prefer POST when I don’t want the status to be change when user resubmits. And GET when it does not matter.
Q:2	Who is the father of PHP and explain the changes in PHP versions?
A:2	Rasmus Lerdorf is known as the father of PHP.PHP/FI 2.0 is an early and no longer supported version of PHP. PHP 3 is the successor to PHP/FI 2.0 and is a lot nicer. PHP 4 is the current generation of PHP, which uses the Zend engine under the hood. PHP 5 uses Zend engine 2 which, among other things, offers many additionalOOP features
Q:3	How can we submit a form without a submit button?
A:3	The main idea behind this is to use Java script submit() function in order to submit the form without explicitly clicking any submit button. You can attach the document.formname.submit() method to onclick, onchange events of different inputs and perform the form submission. you can even built a timer function where you can automatically submit the form after xx seconds once the loading is done (can be seen in online test sites).
Q:4	In how many ways we can retrieve the data in the result set of MySQL using PHP?
A:4	You can do it by 4 Ways1. mysql_fetch_row. 2. mysql_fetch_array 3. mysql_fetch_object 4. mysql_fetch_assoc
Q:5	What is the difference between mysql_fetch_object and mysql_fetch_array?
A:5	mysql_fetch_object() is similar tomysql_fetch_array(), with one difference - an object is returned, instead of an array. Indirectly, that means that you can only access the data by the field names, and not by their offsets (numbers are illegal property names).
Q:6	What is the difference between $message and $$message?
A:6	It is a classic example of PHP’s variable variables. take the following example.$message = “Mizan”;$$message = “is a moderator of PHPXperts.”;$message is a simple PHP variable that we are used to. But the $$message is not a very familiar face. It creates a variable name $mizan with the value “is a moderator of PHPXperts.” assigned. break it like this${$message} => $mizanSometimes it is convenient to be able to have variable variable names. That is, a variable name which can be set and used dynamically.
Q:7	How can we extract string ‘abc.com ‘ from a string ‘http://info@abc.com’ using regular expression of PHP?
A:7	preg_match(”/^http:\/\/.+@(.+)$/”,’http://info@abc.com’,$found); echo $found[1];
Q:8	How can we create a database using PHP and MySQL?
A:8	We can create MySQL database with the use of mysql_create_db(“Database Name”)
Q:9	What are the differences between require and include, include_once and require_once?
A:9	The include() statement includes and evaluates the specified file.The documentation below also applies to require(). The two constructs are identical in every way except how they handle failure. include() produces a Warning while require() results in a Fatal Error. In other words, use require() if you want a missing file to halt processing of the page. include() does not behave this way, the script will continue regardless. The include_once() statement includes and evaluates the specified file during the execution of the script. This is a behavior similar to the include() statement, with the only difference being that if the code from a file has already been included, it will not be included again. As the name suggests, it will be included just once.include_once() should be used in cases where the same file might be included and evaluated more than once during a particular execution of a script, and you want to be sure that it is included exactly once to avoid problems with function redefinitions, variable value reassignments, etc. require_once() should be used in cases where the same file might be included and evaluated more than once during a particular execution of a script, and you want to be sure that it is included exactly once to avoid problems with function redefinitions, variable value reassignments, etc.
Q:10	Can we use include (”abc.PHP”) two times in a PHP page “makeit.PHP”?
A:10	Yes we can use include() more than one time in any page though it is not a very good practice.
Q:11	What are the different tables present in MySQL, which type of table is generated when we are creating a table in the following syntax: create table employee (eno int(2),ename varchar(10)) ?
A:11	Total 5 types of tables we can create 1. MyISAM 2. Heap 3. Merge 4. INNO DB 5. ISAM MyISAM is the default storage engine as of MySQL 3.23 and as a result if we do not specify the table name explicitly it will be assigned to the default engine.
Q:12	Functions in IMAP, POP3 AND LDAP?
A:12	You can find these specific information in PHP Manual.
Q:13	How can I execute a PHP script using command line?
A:13	As of version 4.3.0, PHP supports a new SAPI type (Server Application Programming Interface) named CLI which means Command Line Interface. Just run the PHP CLI (Command Line Interface) program and provide the PHP script file name as the command line argument. For example, “php myScript.php”, assuming “php” is the command to invoke the CLI program. Be aware that if your PHP script was written for the Web CGI interface, it may not execute properly in command line environment.
Q:14	Suppose your Zend engine supports the mode Then how can u configure your PHP Zend engine to support mode ?
A:14	In php.ini file: set short_open_tag=on to make PHP support
Q:15	Shopping cart online validation i.e. how can we configure Paypal, etc.?
A:15	We can find the detail documentation about different paypal integration process at the following site PayPal PHP SDK : http://www.paypaldev.org
Q:16	What is meant by nl2br()?
A:16	Inserts HTML line breaks ( before all newlines in a string string nl2br (string); Returns string with ” inserted before all newlines. For example: echo nl2br(”god bless\n you”) will output “god bless you” to your browser.
Q:17	Draw the architecture of Zend engine?
A:17	The Zend Engine is the internal compiler and runtime engine used by PHP4. Developed by Zeev Suraski and Andi Gutmans, the Zend Engine is an abbreviation of their names. In the early days of PHP4, it worked as follows: The PHP script was loaded by the Zend Engine and compiled into Zend opcode. Opcodes, short for operation codes, are low level binary instructions. Then the opcode was executed and the HTML generated sent to the client. The opcode was flushed from memory after execution.Today, there are a multitude of products and techniques to help you speed up this process. In the following diagram, we show the how modern PHP scripts work; all the shaded boxes are optional. PHP Scripts are loaded into memory and compiled into Zend opcodes.
Q:18	What are the current versions of apache, PHP, and MySQL?
A:18	As of February, 2007 the current versions arePHP: php5.2.1 MySQL: MySQL 5.2 Apache: Apache 2.2.4Note: visit www.php.net, http://dev.mysql.com/downloads/mysql/, www.apache.org to get current versions.
Q:19	What are the reasons for selecting lamp (Linux, apache, MySQL, PHP) instead of combination of other software programs, servers and operating systems?
A:19	All of those are open source resource. Security of Linux is very very more than windows. Apache is a better server that IIS both in functionality and security. MySQL is world most popular open source database. PHP is more faster that asp or any other scripting language.
Q:20	How can we encrypt and decrypt a data present in a MySQL table using MySQL?
A:20	AES_ENCRYPT () and AES_DECRYPT ()
Q:21	How can we encrypt the username and password using PHP?
A:21	The functions in this section perform encryption and decryption, and compression and uncompression: encryption decryption AES_ENCRYT() AES_DECRYPT() ENCODE() DECODE() DES_ENCRYPT() DES_DECRYPT() ENCRYPT() Not available MD5() Not available OLD_PASSWORD() Not available PASSWORD() Not available SHA() or SHA1() Not available Not available UNCOMPRESSED_LENGTH()
Q:22	What are the features and advantages of object-oriented programming?
A:22	One of the main advantages of OO programming is its ease of modification; objects can easily be modified and added to a system there by reducing maintenance costs. OO programming is also considered to be better at modeling the real world than is procedural programming. It allows for more complicated and flexible interactions. OO systems are also easier for non-technical personnel to understand and easier for them to participate in the maintenance and enhancement of a system because it appeals to natural human cognition patterns. For some systems, an OO approach can speed development time since many objects are standard across systems and can be reused. Components that manage dates, shipping, shopping carts, etc. can be purchased and easily modified for a specific system
Q:23	What are the differences between procedure-oriented languages and object-oriented languages?
A:23	Traditional programming has the following characteristics:Functions are written sequentially, so that a change in programming can affect any code that follows it. If a function is used multiple times in a system (i.e., a piece of code that manages the date), it is often simply cut and pasted into each program (i.e., a change log, order function, fulfillment system, etc). If a date change is needed (i.e., Y2K when the code needed to be changed to handle four numerical digits instead of two), all these pieces of code must be found, modified, and tested. Code (sequences of computer instructions) and data (information on which the instructions operates on) are kept separate. Multiple sets of code can access and modify one set of data. One set of code may rely on data in multiple places. Multiple sets of code and data are required to work together. Changes made to any of the code sets and data sets can cause problems through out the system.Object-Oriented programming takes a radically different approach:Code and data are merged into one indivisible item – an object (the term “component” has also been used to describe an object.) An object is an abstraction of a set of real-world things (for example, an object may be created around “date”) The object would contain all information and functionality for that thing (A date object it may contain labels like January, February, Tuesday, Wednesday. It may contain functionality that manages leap years, determines if it is a business day or a holiday, etc., See Fig. 1). Ideally, information about a particular thing should reside in only one place in a system. The information within an object is encapsulated (or hidden) from the rest of the system. A system is composed of multiple objects (i.e., date function, reports, order processing, etc., See Fig 2). When one object needs information from another object, a request is sent asking for specific information. (for example, a report object may need to know what today’s date is and will send a request to the date object) These requests are called messages and each object has an interface that manages messages. OO programming languages include features such as “class”, “instance”, “inheritance”, and “polymorphism” that increase the power and flexibility of an object.
Q:24	What is the use of friend function?
A:24	Sometimes a function is best shared among a number of different classes. Such functions can be declared either as member functions of one class or as global functions. In either case they can be set to be friends of other classes, by using a friend specifier in the class that is admitting them. Such functions can use all attributes of the class which names them as a friend, as if they were themselves members of that class. A friend declaration is essentially a prototype for a member function, but instead of requiring an implementation with the name of that class attached by the double colon syntax, a global function or member function of another class provides the match.
Q:25	What are the differences between public, private, protected, static, transient, final and volatile?
A:25	Public: Public declared items can be accessed everywhere. Protected: Protected limits access to inherited and parent classes (and to the class that defines the item). Private: Private limits visibility only to the class that defines the item. Static: A static variable exists only in a local function scope, but it does not lose its value when program execution leaves this scope. Final: Final keyword prevents child classes from overriding a method by prefixing the definition with final. If the class itself is being defined final then it cannot be extended. transient: A transient variable is a variable that may not be serialized. volatile: a variable that might be concurrently modified by multiple threads should be declared volatile. Variables declared to be volatile will not be optimized by the compiler because their value can change at any time.
Q:26	What are the different types of errors in PHP?
A:26	Three are three types of errors:1. Notices: These are trivial, non-critical errors that PHP encounters while executing a script - for example, accessing a variable that has not yet been defined. By default, such errors are not displayed to the user at all - although, as you will see, you can change this default behavior.2. Warnings: These are more serious errors - for example, attempting to include() a file which does not exist. By default, these errors are displayed to the user, but they do not result in script termination.3. Fatal errors: These are critical errors - for example, instantiating an object of a non-existent class, or calling a non-existent function. These errors cause the immediate termination of the script, and PHP’s default behavior is to display them to the user when they take place.
Q:27	What is the functionality of the function strstr and stristr?
A:27	strstr: Returns part of haystack string from the first occurrence of needle to the end of haystack.If needle is not found, returns FALSE. If needle is not a string, it is converted to an integer and applied as the ordinal value of a character. This function is case-sensitive. For case-insensitive searches, use stristr().
Q:28	What are the differences between PHP 3 and PHP 4 and PHP 5?
A:28	Please read the release notes at http://www.php.net.
Q:29	How can we convert asp pages to PHP pages?
A:29	there are lots of tools available for asp to PHP conversion. you can search Google for that. the best one is available athttp://asp2php.naken.cc./
Q:30	What is the functionality of the function htmlentities?
A:30	Convert all applicable characters to HTML entities This function is identical to htmlspecialchars() in all ways, except with htmlentities(), all characters which have HTML character entity equivalents are translated into these entities.
Q:31	How can we get second of the current time using date function?
A:31	$second = date(”s”);
Q:32	How can we convert the time zones using PHP?
A:32	By using date_default_timezone_get and date_default_timezone_set function on PHP 5.1.0 // Discover what 8am in Tokyo relates to on the East Coast of the US // Set the default timezone to Tokyo time: date_default_timezone_set('Asia/Tokyo'); // Now generate the timestamp for that particular timezone, on Jan 1st, 2000 $stamp = mktime(8, 0, 0, 1, 1, 2000); // Now set the timezone back to US/Eastern date_default_timezone_set('US/Eastern'); // Output the date in a standard format (RFC1123), this will print: // Fri, 31 Dec 1999 18:00:00 EST echo ' ', date(DATE_RFC1123, $stamp) ,' ';?>
Q:33	What is meant by urlencode and urldocode?
A:33	URLencode returns a string in which all non-alphanumeric characters except -_. have been replaced with a percent (%) sign followed by two hex digits and spaces encoded as plus (+) signs. It is encoded the same way that the posted data from a WWW form is encoded, that is the same way as in application/x-www-form-urlencoded media type. urldecode decodes any %## encoding in the given string.
Q:34	What is the difference between the functions unlink and unset?
A:34	unlink() deletes the given file from the file system. unset() makes a variable undefined.
Q:35	How can we register the variables into a session?
A:35	$_SESSION[’name’] = “Mizan”;
Q:36	How can we get the properties (size, type, width, height) of an image using PHP image functions?
A:36	To know the Image type use exif_imagetype () function To know the Image size use getimagesize () function To know the image width use imagesx () function To know the image height use imagesy() function t
Q:37	How can we get the browser properties using PHP?
A:37	By using $_SERVER['HTTP_USER_AGENT'] variable.
Q:38	What is the maximum size of a file that can be uploaded using PHP and how can we change this?
A:38	By default the maximum size is 2MB. and we can change the following setup at php.iniupload_max_filesize = 2M
Q:39	How can we increase the execution time of a PHP script?
A:39	by changing the following setup at php.inimax_execution_time = 30 ; Maximum execution time of each script, in seconds
Q:40	How can we take a backup of a MySQL table and how can we restore it. ?
A:40	To backup: BACKUP TABLE tbl_name[,tbl_name…] TO ‘/path/to/backup/directory’ RESTORE TABLE tbl_name[,tbl_name…] FROM ‘/path/to/backup/directory’mysqldump: Dumping Table Structure and DataUtility to dump a database or a collection of database for backup or for transferring the data to another SQL server (not necessarily a MySQL server). The dump will contain SQL statements to create the table and/or populate the table. -t, –no-create-info Don’t write table creation information (the CREATE TABLE statement). -d, –no-data Don’t write any row information for the table. This is very useful if you just want to get a dump of the structure for a table!
Q:41	How can we optimize or increase the speed of a MySQL select query?
A:41	first of all instead of using select * from table1, use select column1, column2, column3.. from table1 Look for the opportunity to introduce index in the table you are querying. use limit keyword if you are looking for any specific number of rows from the result set.
Q:42	How many ways can we get the value of current session id?
A:42	session_id() returns the session id for the current session.
Q:43	How can we destroy the session, how can we unset the variable of a session?
A:43	session_unregister — Unregister a global variable from the current session session_unset — Free all session variables
Q:44	How can we destroy the cookie?
A:44	Set the cookie in past.
Q:45	How many ways we can pass the variable through the navigation between the pages?
A:45	GET/QueryString POST
Q:46	What is the difference between ereg_replace() and eregi_replace()?
A:46	eregi_replace() function is identical to ereg_replace() except that this ignores case distinction when matching alphabetic characters.eregi_replace() function is identical to ereg_replace() except that this ignores case distinction when matching alphabetic characters.
Q:47	What are the different functions in sorting an array?
A:47	Sort(), arsort(), asort(), ksort(), natsort(), natcasesort(), rsort(), usort(), array_multisort(), and uksort().
Q:48	How can we know the count/number of elements of an array?
A:48	2 ways a) sizeof($urarray) This function is an alias of count() b) count($urarray)
Q:49	What is the PHP predefined variable that tells the What types of images that PHP supports?
A:49	Though i am not sure if this is wrong or not, With the exif extension you are able to work with image meta data.
Q:50	How can I know that a variable is a number or not using a JavaScript?
A:50	bool is_numeric ( mixed var) Returns TRUE if var is a number or a numeric string, FALSE otherwise.or use isNaN(mixed var)The isNaN() function is used to check if a value is not a number.
Q:51	List out some tools through which we can draw E-R diagrams for mysql.
A:51	Case Studio Smart Draw
Q:52	How can I retrieve values from one database server and store them in other database server using PHP?
A:52	we can always fetch from one database and rewrite to another. here is a nice solution of it.$db1 = mysql_connect(”host”,”user”,”pwd”) mysql_select_db(”db1″, $db1); $res1 = mysql_query(”query”,$db1);$db2 = mysql_connect(”host”,”user”,”pwd”) mysql_select_db(”db2″, $db2); $res2 = mysql_query(”query”,$db2);At this point you can only fetch records from you previous ResultSet, i.e $res1 - But you cannot execute new query in $db1, even if you supply the link as because the link was overwritten by the new db.so at this point the following script will fail $res3 = mysql_query(”query”,$db1); //this will failSo how to solve that? take a look below. $db1 = mysql_connect(”host”,”user”,”pwd”) mysql_select_db(”db1″, $db1); $res1 = mysql_query(”query”,$db1); $db2 = mysql_connect(”host”,”user”,”pwd”, true) mysql_select_db(”db2″, $db2); $res2 = mysql_query(”query”,$db2); So mysql_connect has another optional boolean parameter which indicates whether a link will be created or not. as we connect to the $db2 with this optional parameter set to ‘true’, so both link will remain live. now the following query will execute successfully. $res3 = mysql_query(”query”,$db1); Thanks goes to Hasan and Hasin for this solution.
Q:53	List out the predefined classes in PHP?
A:53	Directory stdClass __PHP_Incomplete_Class exception php_user_filter
Q:54	How can I make a script that can be bi-language (supports English, German)?
A:54	You can maintain two separate language file for each of the language. all the labels are putted in both language files as variables and assign those variables in the PHP source. on runtime choose the required language option.
Q:55	What are the difference between abstract class and interface?
A:55	Abstract class: abstract classes are the class where one or more methods are abstract but not necessarily all method has to be abstract. Abstract methods are the methods, which are declare in its class but not define. The definition of those methods must be in its extending class.Interface: Interfaces are one type of class where all the methods are abstract. That means all the methods only declared but not defined. All the methods must be define by its implemented class.
Q:56	How can we send mail using JavaScript?
A:56	JavaScript does not have any networking capabilities as it is designed to work on client site. As a result we can not send mails using JavaScript. But we can call the client side mail protocol mailto via JavaScript to prompt for an email to send. this requires the client to approve it.
Q:57	How can we repair a MySQL table?
A:57	The syntex for repairing a MySQL table is REPAIR TABLENAME, [TABLENAME, ], [Quick],[Extended] This command will repair the table specified if the quick is given the MySQL will do a repair of only the index tree if the extended is given it will create index row by row
Q:58	What are the advantages of stored procedures, triggers, indexes?
A:58	A stored procedure is a set of SQL commands that can be compiled and stored in the server. Once this has been done, clients don’t need to keep re-issuing the entire query but can refer to the stored procedure. This provides better overall performance because the query has to be parsed only once, and less information needs to be sent between the server and the client. You can also raise the conceptual level by having libraries of functions in the server. However, stored procedures of course do increase the load on the database server system, as more of the work is done on the server side and less on the client (application) side.Triggers will also be implemented. A trigger is effectively a type of stored procedure, one that is invoked when a particular event occurs. For example, you can install a stored procedure that is triggered each time a record is deleted from a transaction table and that stored procedure automatically deletes the corresponding customer from a customer table when all his transactions are deleted.Indexes are used to find rows with specific column values quickly. Without an index, MySQL must begin with the first row and then read through the entire table to find the relevant rows. The larger the table, the more this costs. If the table has an index for the columns in question, MySQL can quickly determine the position to seek to in the middle of the data file without having to look at all the data. If a table has 1,000 rows, this is at least 100 times faster than reading sequentially. If you need to access most of the rows, it is faster to read sequentially, because this minimizes disk seeks.
Q:59	What is the maximum length of a table name, database name, and fieldname in MySQL?
A:59	The following table describes the maximum length for each type of identifier. Identifier Maximum Length (bytes) Database 64 Table 64 Column 64 Index 64 Alias 255 There are some restrictions on the characters that may appear in identifiers:
Q:60	How many values can the SET function of MySQL take?
A:60	MySQL set can take zero or more values but at the maximum it can take 64 values
Q:61	What are the other commands to know the structure of table using MySQL commands except explain command?
A:61	describe Table-Name;
Q:62	How many tables will create when we create table, what are they?
A:62	The ‘.frm’ file stores the table definition. The data file has a ‘.MYD’ (MYData) extension. The index file has a ‘.MYI’ (MYIndex) extension,
Q:63	What is the purpose of the following files having extensions 1) .frm 2) .myd 3) .myi? What do these files contain?
A:63	In MySql, the default table type is MyISAM. Each MyISAM table is stored on disk in three files. The files have names that begin with the table name and have an extension to indicate the file type. The ‘.fr m’ file stores the table definition. The data file has a ‘.MYD’ (MYData) extension. The index file has a ‘.MYI’ (MYIndex) extension,
Q:64	What is maximum size of a database in MySQL?
A:64	If the operating system or filesystem places a limit on the number of files in a directory, MySQL is bound by that constraint.The efficiency of the operating system in handling large numbers of files in a directory can place a practical limit on the number of tables in a database. If the time required to open a file in the directory increases significantly as the number of files increases, database performance can be adversely affected. The amount of available disk space limits the number of tables. MySQL 3.22 had a 4GB (4 gigabyte) limit on table size. With the MyISAM storage engine in MySQL 3.23, the maximum table size was increased to 65536 terabytes (2567 – 1 bytes). With this larger allowed table size, the maximum effective table size for MySQL databases is usually determined by operating system constraints on file sizes, not by MySQL internal limits.The InnoDB storage engine maintains InnoDB tables within a tablespace that can be created from several files. This allows a table to exceed the maximum individual file size. The tablespace can include raw disk partitions, which allows extremely large tables. The maximum tablespace size is 64TB. The following table lists some examples of operating system file-size limits. This is only a rough guide and is not intended to be definitive. For the most up-to-date information, be sure to check the documentation specific to your operating system. Operating System File-size LimitLinux 2.2-Intel 32-bit 2GB (LFS: 4GB) Linux 2.4+ (using ext3 filesystem) 4TB Solaris 9/10 16TB NetWare w/NSS filesystem 8TB Win32 w/ FAT/FAT32 2GB/4GB Win32 w/ NTFS 2TB (possibly larger) MacOS X w/ HFS+ 2TB
Q:65	Give the syntax of Grant and Revoke commands?
A:65	The generic syntax for grant is as following > GRANT [rights] on [database/s] TO [username@hostname] IDENTIFIED BY [password] now rights can be a) All privileges b) combination of create, drop, select, insert, update and delete etc.We can grant rights on all databse by using *.* or some specific database by database.* or a specific table by database.table_name username@hotsname can be either username@localhost, username@hostname and username@% where hostname is any valid hostname and % represents any name, the *.* any condition password is simply the password of userThe generic syntax for revoke is as following > REVOKE [rights] on [database/s] FROM [username@hostname] now rights can be as explained above a) All privileges b) combination of create, drop, select, insert, update and delete etc. username@hotsname can be either username@localhost, username@hostname and username@% where hostname is any valid hostname and % represents any name, the *.* any condition
Q:66	Explain Normalization concept?
A:66	The normalization process involves getting our data to conform to three progressive normal forms, and a higher level of normalization cannot be achieved until the previous levels have been achieved (there are actually five normal forms, but the last two are mainly academic and will not be discussed).First Normal FormThe First Normal Form (or 1NF) involves removal of redundant data from horizontal rows. We want to ensure that there is no duplication of data in a given row, and that every column stores the least amount of information possible (making the field atomic).Second Normal FormWhere the First Normal Form deals with redundancy of data across a horizontal row, Second Normal Form (or 2NF) deals with redundancy of data in vertical columns. As stated earlier, the normal forms are progressive, so to achieve Second Normal Form, your tables must already be in First Normal Form.Third Normal Form I have a confession to make; I do not often use Third Normal Form. In Third Normal Form we are looking for data in our tables that is not fully dependant on the primary key, but dependant on another value in the table
Q:67	How can we find the number of rows in a table using MySQL?
A:67	Use this for mysql >SELECT COUNT(*) FROM table_name;
Q:68	How can we find the number of rows in a result set using PHP?
A:68	$result = mysql_query($sql, $db_link); $num_rows = mysql_num_rows($result); echo “$num_rows rows found”;
Q:69	How many ways we can we find the current date using MySQL?
A:69	SELECT CURDATE(); CURRENT_DATE() = CURDATE() for time use SELECT CURTIME(); CURRENT_TIME() = CURTIME()
Q:70	What are the advantages and disadvantages of Cascading Style Sheets?
A:70	External Style SheetsAdvantagesCan control styles for multiple documents at once. Classes can be created for use on multiple HTML element types in many documents. Selector and grouping methods can be used to apply styles under complex contextsDisadvantagesAn extra download is required to import style information for each document The rendering of the document may be delayed until the external style sheet is loaded Becomes slightly unwieldy for small quantities of style definitionsEmbedded Style Sheets Advantages Classes can be created for use on multiple tag types in the document. Selector and grouping methods can be used to apply styles under complex contexts. No additional downloads necessary to receive style information Disadvantages This method can not control styles for multiple documents at once Inline Styles Advantages Useful for small quantities of style definitions. Can override other style specification methods at the local level so only exceptions need to be listed in conjunction with other style methods Disadvantages Does not distance style information from content (a main goal of SGML/HTML). Can not control styles for multiple documents at once. Author can not create or control classes of elements to control multiple element types within the document. Selector grouping methods can not be used to create complex element addressing scenarios
Q:71	What type of inheritance that PHP supports?
A:71	In PHP an extended class is always dependent on a single base class, that is, multiple inheritance is not supported. Classes are extended using the keyword ‘extends’.
Q:72	What is the difference between Primary Key and Unique key?
A:72	Primary Key: A column in a table whose values uniquely identify the rows in the table. A primary key value cannot be NULL. Unique Key: Unique Keys are used to uniquely identify each row in the table. There can be one and only one row for each unique key value. So NULL can be a unique key.There can be only one primary key for a table but there can be more than one unique for a table.
Q:73	The structure of table view buyers is as follows: Field Type Null Key Default Extra user_pri_id int(15) PRI null auto_increment userid varchar(10) YES null the value of user_pri_id the last row 999 then What will happen in the following conditions? Condition1: Delete all the rows and insert another row then. What is the starting value for this auto incremented field user_pri_id , Condition2: Delete the last row(having the field value 999) and insert another row then. What is the value for this auto incremented field user_pri_id
A:73	In both cases let the value for auto increment field be n then next row will have value n+1 i.e. 1000
Q:74	What are the advantages/disadvantages of MySQL and PHP?
A:74	Both of them are open source software (so free of cost), support cross platform. php is faster then ASP and JSP.
Q:75	What is the difference between GROUP BY and ORDER BY in Sql?
A:75	ORDER BY [col1],[col2],…,[coln]; Tels DBMS according to what columns it should sort the result. If two rows will hawe the same value in col1 it will try to sort them according to col2 and so on.GROUP BY [col1],[col2],…,[coln]; Tels DBMS to group results with same value of column col1. You can use COUNT(col1), SUM(col1), AVG(col1) with it, if you want to count all items in group, sum all values or view average
Q:76	What is the difference between char and varchar data types?
A:76	Set char to occupy n bytes and it will take n bytes even if u r storing a value of n-m bytes Set varchar to occupy n bytes and it will take only the required space and will not use the n bytes eg. name char(15) will waste 10 bytes if we store ‘mizan’, if each char takes a byte eg. name varchar(15) will just use 5 bytes if we store ‘mizan’, if each char takes a byte. rest 10 bytes will be free.
Q:77	What is the functionality of md5 function in PHP?
A:77	Calculate the md5 hash of a string. The hash is a 32-character hexadecimal number. I use it to generate keys which I use to identify users etc. If I add random no techniques to it the md5 generated now will be totally different for the same string I am using.
Q:78	How can I load data from a text file into a table?
A:78	you can use LOAD DATA INFILE file_name; syntax to load data from a text file. but you have to make sure thata) data is delimited b) columns and data matched correctly
Q:79	How can we know the number of days between two given dates using MySQL?
A:79	SELECT DATEDIFF(’2007-03-07′,’2005-01-01′);
Q:80	How can we know the number of days between two given dates using PHP?
A:80	$date1 = date(’Y-m-d’); $date2 = ‘2006-08-15′; $days = (strtotime($date1) - strtotime($date2)) / (60 * 60 * 24);

1. What does a special set of tags do in PHP? - The output is displayed directly to the browser.
2. What’s the difference between include and require? - It’s how they handle failures. If the file is not found by require(), it will cause a fatal error and halt the execution of the script. If the file is not found by include(), a warning will be issued, but execution will continue.
3. I am trying to assign a variable the value of 0123, but it keeps coming up with a different number, what’s the problem? - PHP Interpreter treats numbers beginning with 0 as octal. Look at the similar PHP interview questions for more numeric problems.
4. Would I use print "$a dollars" or "{$a} dollars" to print out the amount of dollars in this example? - In this example it wouldn’t matter, since the variable is all by itself, but if you were to print something like "{$a},000,000 mln dollars", then you definitely need to use the braces.
5. How do you define a constant? - Via define() directive, like define ("MYCONSTANT", 100);
6. How do you pass a variable by value? - Just like in C++, put an ampersand in front of it, like $a = &$b
7. Will comparison of string "10" and integer 11 work in PHP? - Yes, internally PHP will cast everything to the integer type, so numbers 10 and 11 will be compared.
8. When are you supposed to use endif to end the conditional statement? - When the original if was followed by : and then the code block without braces.
9. Explain the ternary conditional operator in PHP? - Expression preceding the ? is evaluated, if it’s true, then the expression preceding the : is executed, otherwise, the expression following : is executed.
10. How do I find out the number of parameters passed into function? - func_num_args() function returns the number of parameters passed in.
11. If the variable $a is equal to 5 and variable $b is equal to character a, what’s the value of $$b? - 100, it’s a reference to existing variable.
12. What’s the difference between accessing a class method via -> and via ::? - :: is allowed to access methods that can perform static operations, i.e. those, which do not require object initialization.
13. Are objects passed by value or by reference? - Everything is passed by value.
14. How do you call a constructor for a parent class? - parent::constructor($value)
15. What’s the special meaning of __sleep and __wakeup? - __sleep returns the array of all the variables than need to be saved, while __wakeup retrieves them.
16. Why doesn’t the following code print the newline properly? $str = ‘Hello, there.\nHow are you?\nThanks for visiting TechInterviews’;
    print $str;
    ?>
    Because inside the single quotes the \n character is not interpreted as newline, just as a sequence of two characters - \ and n.
17. Would you initialize your strings with single quotes or double quotes? - Since the data inside the single-quoted string is not parsed for variable substitution, it’s always a better idea speed-wise to initialize a string with single quotes, unless you specifically need variable substitution.
18. How come the code works, but doesn’t for two-dimensional array of mine? - Any time you have an array with more than one dimension, complex parsing syntax is required. print "Contents: {$arr[1][2]}" would’ve worked.
19. What is the difference between characters \023 and \x23? - The first one is octal 23, the second is hex 23.
20. With a heredoc syntax, do I get variable substitution inside the heredoc contents? - Yes.
21. I want to combine two variables together:

22.   $var1 = 'Welcome to ';

23.   $var2 = 'TechInterviews.com';

What will work faster? Code sample 1:

$var 3 = $var1.$var2;

Or code sample 2:

$var3 = "$var1$var2";

Both examples would provide the same result - $var3 equal to "Welcome to TechInterviews.com". However, Code Sample 1 will work significantly faster. Try it out with large sets of data (or via concatenating small sets a million times or so), and you will see that concatenation works significantly faster than variable substitution.

24. For printing out strings, there are echo, print and printf. Explain the differences. - echo is the most primitive of them, and just outputs the contents following the construct to the screen. print is also a construct (so parentheses are optional when calling it), but it returns TRUE on successful output and FALSE if it was unable to print out the string. However, you can pass multiple parameters to echo, like:

and it will output the string "Welcome to TechInterviews!" print does not take multiple parameters. It is also generally argued that echo is faster, but usually the speed advantage is negligible, and might not be there for future versions of PHP. printf is a function, not a construct, and allows such advantages as formatted output, but it’s the slowest way to print out data out of echo, print and printf.

25. I am writing an application in PHP that outputs a printable version of driving directions. It contains some long sentences, and I am a neat freak, and would like to make sure that no line exceeds 50 characters. How do I accomplish that with PHP? - On large strings that need to be formatted according to some length specifications, use wordwrap() or chunk_split().
26. What’s the output of the ucwords function in this example?

27.     $formatted = ucwords("TECHINTERVIEWS IS COLLECTION OF INTERVIEW QUESTIONS");

   print $formatted;

What will be printed is TECHINTERVIEWS IS COLLECTION OF INTERVIEW QUESTIONS.
ucwords() makes every first letter of every word capital, but it does not lower-case anything else. To avoid this, and get a properly formatted string, it’s worth using strtolower() first.

28. What’s the difference between htmlentities() and htmlspecialchars()? - htmlspecialchars only takes care of <, >, single quote ‘, double quote " and ampersand. htmlentities translates all occurrences of character sequences that have different meaning in HTML.
29. What’s the difference between md5(), crc32() and sha1() crypto on PHP? - The major difference is the length of the hash generated. CRC32 is, evidently, 32 bits, while sha1() returns a 128 bit value, and md5() returns a 160 bit value. This is important when avoiding collisions.
30. So if md5() generates the most secure hash, why would you ever use the less secure crc32() and sha1()? - Crypto usage in PHP is simple, but that doesn’t mean it’s free. First off, depending on the data that you’re encrypting, you might have reasons to store a 32-bit value in the database instead of the 160-bit value to save on space. Second, the more secure the crypto is, the longer is the computation time to deliver the hash value. A high volume site might be significantly slowed down, if frequent md5() generation is required.
31. How do you match the character ^ at the beginning of the string? - ^\^