Top PHP Interview Questions in 2024

30. How can you concatenate two strings in PHP?
For this, you would require a dot (.) operator, and you can write the following code: 

<?php $string1=”Hello World“; $string2=”in PHP”; echo $string1 . ” ” . $string2; ?> 

The output of this will be: Hello World in PHP

31. What is the use of Memcache?

• Firstly, Memcache significantly minimizes the load time of the database by reducing the number of database calls.  
• Secondly, it improves the user experience with improved data access time.  
• And thirdly, it increases the speed of the website by storing the object in dynamic memory. 

32. Write down the syntax to create an array for a group of items inside the HTML form.

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

33. Why are traits used in PHP?   

PHP does not support multiple inheritances. A child class can only inherit from a single parent. Due to this, traits are used to minimize the limitation of single inheritance in PHP. It is a group of various methods that allow developers to reuse sets of methods. Below is an example of using multiple traits in PHP:  

<?php
trait message1 {
public function msg1() {
echo “OOP is fun! “;
}
}

trait message2 {
public function msg2() {
echo “OOP reduces code duplication!”;
}
}

class Welcome {
use message1;
}

class Welcome2 {
use message1, message2;
}

$obj = new Welcome();
$obj->msg1();
echo “<br>”;

$obj2 = new Welcome2();
$obj2->msg1();
$obj2->msg2();
?>
Source– W3 School 

34. Explain the significance of PSR.
It is a PHP Standard Recommendation (PSR). A set of guidelines that ensures code consistency, collaboration within the community, and interoperability of projects in PHP. 

35. How do you use comments in PHP?

Comments can be used in two different ways:

Single line: <?php
# This is a comment
echo “Single-line comment”;
?>

Multiple line: <?php
/*
This is
a
Multi-line
Comment
In PHP;
*/
echo “Multi-line comment”;
?>

36. Define Persistent Cookies.
It is a type of cookie stored on the user’s device that contains the details of the user’s sign-in information saved previously, preferences, and settings. To set the persistent cookie in PHP,  you can write the following code: 

setcookie (“user”, “Ansel Elgort”, time() + 3600 * 24 * 30); 

37. Name some of the popular content management systems built using PHP.

• Magneto  
• WordPress  
• Joomla  
• Durpal 

38. Write steps to execute a PHP script from the Command Line

• Open your command-line window. 
• Go to the directory where the PHP files are located. 
• Run the PHP code using the php file_name.php command line. 
• Now you need to start the server using this command: php -S localhost:port -t your_folder/. 

39. Can you show how to find duplicate email records in the user table?
SELECT u1.first_name, u1.last_name, u1.email FROM users as u1 

INNER JOIN ( 

SELECT email FROM users GROUP BY email HAVING count(id) > 1 

) u2 ON u1.email = u2.email;

40. What is the difference between mysql_fetch_array(), mysql_fetch_object(), and mysql_fetch_row()? 

• mysql_fetch_array(): It fetches one row of data according to the result specified in the result identifier. And each result column stores an array offset.  
• mysql_fetch_object(): It fetches the result row as an object. If there are no more rows to fetch, then it returns false.  
• mysql_fetch_array(): It fetches the result row as a numeric array or associative array. 

41. Show how to establish a database connection in PHP.

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

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

// Check connection
if ($conn->connect_error) {
die(“Connection failed: ” . $conn->connect_error);
}
echo “Connected successfully”;
?>
Source– W3 School

42. How can we redirect page in PHP?

We can redirect pages in PHP using header functions.

By using the header function in PHP, we can send the raw HTTP header to the client.

Syntax for redirecting pages using header functions:

header( $header, $replace, $http_response_code )

<?php

header(“Location: http://www.redirect.com/another-page.php”);

exit();

?>

43. What is the Magic Method?

The magic method is the set of member functions available for all instances of the class. It is always defined within the class. The following are the magic methods:  

• __construct()  
• __destruct()  
• __set()  
• __get()  
• __call()  
• __toString()  
• __sleep()  
• __wakeup()  
• __isset()  
• __unset()  
• __autoload()  
• __clone()  

44. How does JavaScript interact with PHP?  

PHP, being a scripting language, can easily generate JavaScript variables and then execute them in the browser.

45. Write a simple program using the While Loop.  

my_qry = mysql_query(“SELECT * FROM `users` WHERE `u_id`=’1′; “);

while($result = mysql_fetch_array($my_qry))

{

echo $result[‘First_name’.].”<br/>”;

}

46. How does a client communicate with the web server?

The client can communicate with the server in two different ways:

•GET Method

•POST Method

•GET Method: <?php

if( $_GET[“name”] || $_GET[“age”] ) {

echo “Welcome “. $_GET[‘name’]. “<br />”;

echo “You are “. $_GET[‘age’]. ” years old.”;

exit();

}

?>

<html>

<body>

<form action = “<?php $_PHP_SELF ?>” method = “GET”>

Name: <input type = “text” name = “name” />

Age: <input type = “text” name = “age” />

<input type = “submit” />

</form>

</body>

</html>

•POST Method: <?php

if( $_POST[“name”] || $_POST[“age”] ) {

if (preg_match(“/[^A-Za-z’-]/”,$_POST[‘name’] )) {

die (“invalid name and name should be alpha”);

}

Echo “Welcome “. $_POST[‘name’]. “<br />”;

echo “You are “. $_POST[‘age’]. ” years old.”;

exit();

}

?>

<html>

<body>

<form action = “<?php $_PHP_SELF ?>” method = “POST”>

Name: <input type = “text” name = “name” />

Age: <input type = “text” name = “age” />

<input type = “submit” />

</form>

</body>

</html> 

47. How can we set infinite execution time in PHP?

We can do this by adding the set_time_limit(0) function to the beginning of a script.

48. How to create a text file in 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 testn” );

fclose( $file );

49. Can you show how to get an IP Address from the Client Machine?

function getRealIpAddr()
{
if (!empty($_SERVER[‘HTTP_CLIENT_IP’]))
{
$ip=$_SERVER[‘HTTP_CLIENT_IP’];
}
elseif (!empty($_SERVER[‘HTTP_X_FORWARDED_FOR’]))
{
$ip=$_SERVER[‘HTTP_X_FORWARDED_FOR’];
}
else
{
$ip=$_SERVER[‘REMOTE_ADDR’];
}
return $ip;
}