Php Interview

Front 1

What is PHP?

Back 1

- Server Side scripting Object oriented language
- common for web applications

Front 2

whats echo

Back 2

used to print data in webpage

Front 3

how to include a file in php page?

Back 3

- use include() or require() function.
- use filename as parameter

Front 4

Whats the difference between include() and require()

Back 4

- if using require() and file not found, will cause fatal error
- if using include() and file not found, warning will be issued but still execute

Front 5

Difference between require_once(), require(), and include()

Back 5

-require() includes and evaluates a specific file
- require_once() does that if it has not been included before. Recommended when you want to include a file where there are lots of functions for example

Front 6

Difference between POST and GET methods

Back 6

- GET: 1024 bytes sent using this method
- POST: large amounts of data and POST is more secure method

Front 7

Declaring an array

Back 7

var $arr = array('apple', 'grape', 'lemon');

Front 8

What is the use of 'print' in PHP

Back 8

not a real function. just a language construct. can be used without parantheses

print 'PHP Interview'

Front 9

What is the use of in_array()

Back 9

in_array used to check if a value exists in an array

Front 10

what is the use of count()?

Back 10

count() is used to count all elements in an array, or something in an object

Front 11

Difference between session and cookie?

Back 11

- sessions are stored on server, holds multiple variables, users don't have access
- cookies are stored on personal computer, can't hold multple variables

Front 12

how to set cookies?

Back 12

Setcookie("sample", "ram", time()+3600);

Front 13

How to retrieve a Cookie Value

Back 13

echo $_COOKIE["user"];

Front 14

How to create a session, set value in session and remove data from session?

Back 14

Create Session: session_start();
Set value into session: $_SESSION['USER_ID'];
Remove Data from a session: unset($_SESSION['USER_ID'];

Front 15

What types of loops exist in php?

Back 15

for, while, do while, foreach

Front 16

How to create mysql connection?

Back 16

mysql_connect(servername, username, password);

Front 17

How to select a database?

Back 17

mysql_select_db($db_name);

Front 18

How to execute an sql query? How to fetch its result?

Back 18

$my_qry = mysql_query("SELECT * FROM 'users' WHERE 'u_id' = '1'; ");
$result = mysql_fetch_array($my_qry);
echo $result['First_name'];

Front 19

Write a program w/ while loop

Back 19

$my_qry = mysql_query("SELECT * FROM `users` WHERE `u_id`='1'; ");
while($result = mysql_fetch_array($my_qry))
{
echo $result['First_name'.]."<br/>";
}

Front 20

Ways we can retrieve data in result set of MySQL using PHP?

Back 20

mysql_fetch_assoc
mysql_fetch_row
mysql_fetch_object
mysql_fetch_array

Front 21

Whats the use of the explode() function?

Back 21

Syntax: array explode (string $delimiter, string $string [' int $limit] );

breaks string into array. Each of the array elemnts is a substring of string formed by splitting it on boundaries formed by the string delimiter

Front 22

difference between explode() and split()

Back 22

- split(): splits string into array by regular expression
- explode(): splits string into array by string()

Front 23

what is the use of mysql_real_escape_string() function?

Back 23

- used to escape special characters in a string for use in an SQL statement

Front 24

Write down the code for save an uploaded file in php.

Back 24

if ($_FILES["file"]["error"] == 0)
{
move_uploaded_file($_FILES["file"]["tmp_name"],
"upload/" . $_FILES["file"]["name"]);
echo "Stored in: " . "upload/" . $_FILES["file"]["name"];
}

Front 25

How to create a text file in php?

Back 25

$filename = "/home/user/guest/newfile.txt";
$file = fopen( $filename, "w" );
if( $file == false )
{
echo ( "Error in opening new file" ); exit();
}
fwrite( $file, "This is a simple test\n" );
fclose( $file );

Front 26

How to strip whitespace (or other characters) from the beginning and end of a string?

Back 26

The trim() function removes whitespaces or other predefined characters from both sides of a string.

Front 27

What is the use of header() function in php?

Back 27

The header() function sends a raw HTTP header to a client browser.Remember that this function must be called before sending the actual out put.For example, You do not print any HTML element before using this function.

Front 28

How to redirect a page in php?

Back 28

The following code can be used for it, header("Location:index.php");

Front 29

How stop the execution of a php script?

Back 29

exit()

Front 30

How to set a page as a home page in a php based website?

Back 30

index.php is the default name of home page in php based sites

Front 31

How to find the length of a string?

Back 31

strlen() is used to find length of string

Front 32

what is the use of rand()

Back 32

- It is used to generate random numbers.
- If called without the arguments it returns a pseudo-random integer between 0 and getrandmax().
- If you want a random number between 6 and 12 (inclusive), for example, use rand(6, 12).
- This function does not generate cryptographically safe values, and should not be used for cryptographic uses.
-If you want a cryptographically secure value, consider using openssl_random_pseudo_bytes() instead.

Front 33

What is the use of isset() in php?

Back 33

-used to determine if a variable is set and is not NULL

Front 34

difference between mysql_fetch_array vs msql_fetch_assoc()?

Back 34

fetch assoc: fetches a result row as an associative array
fetch array: fetches an associative array, numeric array, or both

Front 35

what is meant by an associative array?

Back 35

associative arrays are arrays that use string keys

Front 36

What is the importance of "method" attribute in a html form?

Back 36

"method" attribute determines how to send the form-data into the server.There are two methods, get and post. The default method is get.This sends the form information by appending it on the URL.Information sent from a form with the POST method is invisible to others and has no limits on the amount of information to send.

Front 37

What is the importance of "action" attribute in a html form?

Back 37

determines where to send form-data in the form submission

Front 38

whats the use of enctype attribute in a html form?

Back 38

determines how the form-data should be encodedwhen submitting it to the server
-We need to set enctype as "multipart/form-data" when we are using a form for uploading files

Front 39

How to create an array of a group of items inside an HTML form?

Back 39

We can create input fields with same name for "name" attribute with squire bracket at the end of the name of the name attribute, It passes data as an array to PHP.

For instance :

<input name="MyArray[]" /> <input name="MyArray[]" /> <input name="MyArray[]" /> <input name="MyArray[]" />

Front 40

Define Object-Oriented Methodology

Back 40

Object orientation is a software/Web development methodology that is based on the modeling a real world system.An object is the core concept involved in the object orientation. An object is the copy of the real world enity.An object oriented model is a collection of objects and its inter-relationships

Front 41

How do you define a constant?

Back 41

Using define() directive, like define ("MYCONSTANT",150)

Front 42

How send email using php?

Back 42

To send email using PHP, you use the mail() function.This mail() function accepts 5 parameters as follows (the last 2 are optional). You need webserver, you can't send email from localhost. eg : mail($to,$subject,$message,$headers);

Front 43

How to find current date and time?

Back 43

The date() function provides you with a means of retrieving the current date and time, applying the format integer parameters indicated in your script to the timestamp provided or the current local time if no timestamp is given. In simplified terms, passing a time parameter is optional - if you don't, the current timestamp will be used.

Front 44

Difference between mysql_connect and mysql_pconnect?

Back 44

There is a good page in the php manual on the subject, in short mysql_pconnect() makes a persistent connection to the database which means a SQL link that do not close when the execution of your script ends. mysql_connect()provides only for the databasenewconnection while using mysql_pconnect , the function would first try to find a (persistent) link that's already open with the same host, username and password. If one is found, an identifier for it will be returned instead of opening a new connection... the connection to the SQL server will not be closed when the execution of the script ends. Instead, the link will remain open for future use.

Front 45

What is the use of "ksort" in php?

Back 45

It is used for sort an array by key in reverse order.

Front 46

What is the difference between $var and $$var?

Back 46

They are both variables. But $var is a variable with a fixed name. $$var is a variable who's name is stored in $var. For example, if $var contains "message", $$var is the same as $message.

Front 47

What are the encryption techniques in PHP?

Back 47

MD5: PHP implements the MD5 hash algorithm using the md5 function.

eg : $encrypted_text = md5 ($msg);

mcrypt_encrypt: string mcrypt_encrypt ( string $cipher , string $key , string $data , string $mode [, string $iv ] );

Encrypts plaintext with given parameters

Front 48

what is the use of the function htmlentities?

Back 48

htmlentities 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.

Front 49

How to delete a file from the system?

Back 49

Unlink() deletes the given file from the file system.

Front 50

How to get the value of current session id?

Back 50

session_id() function returns the session id for the current session.

Front 51

What are the differences between mysql_fetch_array(), mysql_fetch_object(), mysql_fetch_row()?

Back 51

Mysql_fetch_array Fetch a result row as an associative array, a numeric array, or both.
mysql_fetch_object ( resource result ) Returns an object with properties that correspond to the fetched row and moves the internal data pointer ahead. Returns an object with properties that correspond to the fetched row, or FALSE if there are no more rows
mysql_fetch_row() fetches one row of data from the result associated with the specified result identifier. The row is returned as an array. Each result column is stored in an array offset, starting at offset 0.

Front 52

What are the different types of errors in PHP?

Back 52

Here are three basic types of runtime errors in PHP:

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 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.

Front 53

What is SQL Injection?

Back 53

SQL injection is a malicious code injection technique.It exploiting SQL vulnerabilities in Web applications

Front 54

What is x+ mode in fopen() used for?

Back 54

Read/Write. Creates a new file. Returns FALSE and an error if file already exists

Front 55

How to find the position of the first occurrence of a substring in a string?

Back 55

strpos() is used to find the position of the first occurrence of a substring in a string

Front 56

What is PEAR?

Back 56

PEAR is a framework and distribution system for reusable PHP components.The project seeks to provide a structured library of code, maintain a system for distributing code and for managing code packages, and promote a standard coding style.PEAR is broken into three classes: PEAR Core Components, PEAR Packages, and PECL Packages. The Core Components include the base classes of PEAR and PEAR_Error, along with database, HTTP, logging, and e-mailing functions. The PEAR Packages include functionality providing for authentication, networking, and file system features, as well as tools for working with XML and HTML templates.

Front 57

Distinguish between urlencode and urldecode?

Back 57

This method is best when encode a string to used in a query part of a url. it returns a string in which all non-alphanumeric characters except -_. have replece with a percentege(%) sign . the urldecode->Decodes url to encode string as any %and other symbole are decode by the use of the urldecode() function.

I will come up with more PHP interview questions and answers in second part of this post.