PHP Interview questions and answers for freshers and experienced

 

 

Top PHP interview questions and answers.
Below are  compiled list of the  latest PHP interview questions and answers.Before attend interview , interviewer need to read all below basic/advance  technical PHP interview questions and answers for freshers and experienced.

 

PHP Interview questions and answers for freshers and experienced

 

 

What is PHP ?

PHP is the loosely scripting language to server side. There are different types of frameworks and CMS available in PHP for creating dynamics websites. whether non  technical person can create websites on CMS (wordpress,joomla etc). All OOPS concept are supported in PHP.

How to  use “echo” in phpb ?

echo is used to print a string in the web,

Ex: <?php echo ‘hi’; ?> ,

How to include a file into  php page ?

We include a file using “include() ” or “require()” function with file path as its parameter.

What is  the difference between include and require ?

If the file is not available into require(), it will cause a fatal error and halt the execution of the script.

If the file is not available into include(), a warning will be issued, but execution will continue.

Please explain the below function 
require_once(), require(), include().

require() includes and evaluates a relevent file, while require_once() does that only if it has not been included before (on the same page). So, require_once() is recommended to use when you want to include a file where you have a lot of functions for example. This way you make sure you don’t include the file more times and you will not get the “function re-declared” error.

Differences between GET and POST methods ?

We can send 1024 bytes  in GET method but POST method can transfer large amount of data and POST is the much more  secure method than GET method .Because In GET methods , we send data into browser.

How to defined an array in php?

Eg :

$arr = array(‘ram’, ‘mohan’, ‘ganesh’);

How to  use of ‘print’ in php ?

It is a language construct. So we can use without parentheses with its argument list.

Ex:

print(‘hi how are you’);
print ‘welcome ‘);

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

in_array used to checks if a value exists in an array. If it is available then returns true otherwise return false.

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

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

What’s the difference between include and require?

It’s how they handle failures. If the file is not available 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.

What is the difference between Session and Cookie in PHP?

The main difference between sessions and cookies is that sessions are objects that  stored on the server, and cookies are stored on the client’s computers in the text file format. Cookies can’t hold multiple variable while session can hold multiple variables..We can set expiry for a cookie,The session only remains active as long as the browser is open.Users do not have access to the data you stored in Session,Since it is stored in the server.Session is mainly used for login/logout purpose while cookies using for user activity tracking temporary or permanent.

How to set cookies in PHP?

Setcookie(“name”, “value”, time()+3600);

How to Fetch a Cookie Value ?

eg : echo $_COOKIE[“name”];

How to create a session? How to set a value in session ? How to Remove data from a session?

Create session : session_start();   on the top of page
Set value into session : $_SESSION[‘name’]=’foo’;
Remove data from a session : unset($_SESSION[‘USER_ID’];

 Types of loops exist in php?

for,while,do while and foreach

How to make a mysql connection in php ?

<?php
$servername = “localhost”;
$username = “user”;
$password = “pwd”;

try {
$conn = new PDO(“mysql:host=$servername;dbname=myDB”, $username, $password);
// set the PDO error mode to exception
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
echo “Connected successfully”;
}
catch(PDOException $e)
{
echo “Connection failed: ” . $e->getMessage();
}
?>

Example (MySQLi Object-Oriented)

<?php
$servername = “localhost”;
$username = “username”;
$password = “password”;
$dbname = “myDB”; // Optional

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);

// Check connection
if ($conn->connect_error) {
die(“Connection failed: ” . $conn->connect_error);
}
echo “Connected successfully”;
?>

Example (MySQLi Procedural)

<?php
$servername = “localhost”;
$username = “username”;
$password = “password”;
$dbname = “myDB”; // Optional

// Create connection
$conn = mysqli_connect($servername, $username, $password, $dbname);

// Check connection
if (!$conn) {
die(“Connection failed: ” . mysqli_connect_error());
}
echo “Connected successfully”;
?>

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

Example (MySQLi Object-oriented)

<?php
$sql = “SELECT id, firstname, lastname FROM table”;
$result = $conn->query($sql); // execute sql query

if ($result->num_rows > 0) {
// output data of each row
while($row = $result->fetch_assoc()) { // fetch data
echo “id: ” . $row[“id”]. ” – Name: ” . $row[“firstname”]. ” ” . $row[“lastname”]. “<br>”;
}
} else {
echo “0 results”;
}
?>

Method 1:USE PDO query method

<?php

$stmt = $db->query(‘SELECT id FROM Employee’);
$row_count = $stmt->rowCount();
echo $row_count.’ rows selected’;

?>

Method 2: Statements With Parameters

$stmt = $db->prepare(“SELECT id FROM Employee WHERE name=?”);
$stmt->execute(array($name));
$rows = $stmt->fetchAll(PDO::FETCH_ASSOC);

How to write  a program using while loop

<?php
$x = 1;

while($x <= 5) {
echo “The number is: $x <br>”;
$x++;
}
?>

How we can fetch the data in the result set of MySQL using PHP?
MySQLi methods

1. mysqli_fetch_row
2. mysqli_fetch_array
3. mysqli_fetch_object
4. mysqli_fetch_assoc

Uing PDO methods

1. PDOStatement::fetch(PDO::FETCH_ASSOC)
2. PDOStatement::fetch(PDO::FETCH_OBJ)
3. PDOStatement::fetch()
4. PDOStatement::fetch(PDO::FETCH_NUM)

How to  use of explode() function ?

Syntax : array explode ( string $delimiter , string $string [, int $limit ] );
This function breaks a string into an array. Each of the array elements is a substring of string formed by splitting it on boundaries formed by the string delimiter.

What is the difference between explode() and str_split() functions?

str_split function  splits string into array using  by regular expression. Explode splits a string into array by  using string.

How to  use of mysql_real_escape_string() function in Mysql?

It is used to escapes special characters from string for use in an SQL statement
Write down the code for save an uploaded file in php.
<?php
if ($_FILES[“file”][“error”] == 0)
{
move_uploaded_file($_FILES[“file”][“tmp_name”],
“upload/” . $_FILES[“file”][“name”]);
echo “Stored in: ” . “upload/” . $_FILES[“file”][“name”];
}
?>
How to create a text file in php?

<?php
$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 );
?>
How to strip whitespace (or other characters) from the beginning and end of a string ?

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

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

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 just before using this function.

How to redirect a page in php?

From the help of The following code can ,

header(“Location:index.php”);

How stop the execution of a php scrip ?

exit() function is used to hault the execution of a page.

How to set a page as a home page in a php folder?

index.php is the default name of the home page in php folder.

How to get the length of a string?

strlen() function is used to find the length of a string.

Define the  rand() in php?

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.

what is the  isset() in php?

This function is used to determine if a variable is set and is not NULL.

What is the difference between mysql_fetch_array() and mysql_fetch_assoc() ?

mysql_fetch_assoc function Fetch a result row as an associative array, While mysql_fetch_array() fetches an associative array, a numeric array, or both

What is mean by an associative array?

Associative arrays are arrays that use string keys is called associative arrays.

What is the importance of “method” attribute in a html form tag ?

“method” attribute determines how to send the form-data to 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.

What is the importance of “action” attribute in a html form tag ?

The action attribute determines where to send the form-data in the form submission.

What is the use of “enctype” attribute in a html form tag?

The enctype attribute determines how the form-data should be encoded when submitting it to the server. We need to set enctype as “multipart/form-data” when we are using a form for uploading files process.

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

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=”animal[]” id=”cat” />
<input name=”animal[]” id=”rat” />
<input name=”animal[]” id=”lion” />
<input name=”animal[]” id=”snake” />
Define Object-Oriented Methodology

Object orientation is a software programming 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.

 Define a constant?

Define() directive, like

define (“MYCONSTANT”,150);

How to send email using php ?

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 :
<?php
mail($to,$subject,$message,$headers);
?>
mcrypt_encrypt :- string mcrypt_encrypt ( string $cipher , string $key , string $data , string $mode [, string $iv ] );
Encrypts plaintext with given parameters.

Find current date and time ?

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.

What is Difference between mysql_connect and mysql_pconnect?

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, then  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.

What is the use of “ksort” in php array ?

It is used for sort an array by key in reverse order.
What is the difference between $var and $$var?

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.
What are the encryption techniques in PHP

MD5 PHP implements the MD5 hash algorithm using the md5 function,
<?php
$encrypted_text = md5 ($msg);
?>

What is the use of the function htmlentities?

htmlentities Convert all applicable characters  into  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.
How to delete a file from the system

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

How to get the value of current session id?

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

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

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.

 

what is sql injection ?

An SQL injection (SQLi) refers to an computer attack in which malicious code is embedded in a loosely-designed application and then passed to the database. The malicious data then altering database query results or actions that should never have been executed.

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

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

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

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

What is PEAR?

PEAR is known as PHP Extension and Application Repository.The logics behind the Pear was to reuse the existing code and packages, to promote a standard coding style throughout. PEAR also provided a way to install PECL(PHP Extension Community Library) extensions.
In many ways it is most similar to ‘Composer'(php’s de facto package and dependency manager).Just as Composer downloads and installs packages from packagist.com . Pear could be downloads the packages from pear.php.net.

What is difference between urlencode and urldecode in php?

urlencode() function returns the URL encoded version of the given string. URL encoding coding converts special characters into % signs followed by two hex digits.
For example: urlencode(”10.00%”) will return “10%2E00%25&#8243;. URL encoded strings are safe to beused as part of URLs.

urldecode() function returns the URL decoded version of the given string.

How many  different errors in PHP?

There are diffferent types of error in PHP. It is defined in below :

Warnings:
When we try to include () file which is not available. These errors are showed to the user by default but they will not result in haluting the script.
Notices:
This types of  errors are non-critical and trivial errors that come across while executing the script in PHP. Example: trying to access the variable but  this is not defined. These types of errors are not showed to the users by default even if the default behavior is changed.
Fatal errors:
This types of erros  are critical errors. Example: instantiating the  object of a class which does not exist or a non-existent function is called. These errors results in haulting the script immediately and default behavior of PHP is shown to them when they take place.

 

 

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