Top 15+ Advanced PHP Interview Questions & Answers in 2023


1. Is PHP a case-sensitive scripting language?

The answer to this is both yes and no. Variables and their declaration in PHP are completely case sensitive while function names are not.

For example, user-defined functions in PHP can be defined in uppercase but later referred to in lowercase, and it would still function normally.

Next up on these PHP interview questions for freshers, you need to understand what PEAR is.

2. How is a PHP script executed?

PHP scripts can be easily executed from the command-line interface (CLI). The syntax is as follows:php filename.php

Here, filename refers to the file that contains scripts. The extension .php is needed alongside the filename.

3. What are the variable-naming rules you should follow in PHP?

There are two main rules that you have to follow when naming a variable in PHP. They are as follows:

Variables can only begin with letters or underscores.
Special characters such as +, %, -, &, etc. cannot be used.

4. What is NULL in PHP?

NULL is a special data type in PHP used to denote the presence of only one value, NULL. You cannot assign any other value to it.

NULL is not case sensitive in PHP and can be declared in two ways as shown below:

$var = NULL:


$var = null;

Both of the above syntaxes work fine in PHP

5. What is the use of the constant() function in PHP?

The constant() function is used to retrieve the values predefined in a constant variable. It is used especially when you do not know the name of the variable.

6. What are the various constants predefined in PHP?

PHP consists of many constants, and following are some of the widely used ones:

  • _METHOD_: Represents the class name
  • _CLASS_: Returns the class name
  • _FUNCTION_: Denotes the function name
  • _LINE_: Denotes the working line number
  • _FILE_: Represents the path and the file name

7. How are two objects compared in PHP?

PHP provides you with the ‘==’ operator, which is used to compare two objects at a time. This is used to check if there is a common presence of attributes and values between the objects in comparison.

The ‘===’ operator is also used to compare if both objects in consideration are referencing to the same class.

8. What are some of the popular frameworks in PHP?

There are many frameworks in PHP that are known for their usage. Following are some of them:

  • CodeIgniter
  • CakePHP
  • Laravel
  • Zend
  • Phalcon
  • Yii 2

9. Do you need to compile PHP programs before execution like C++?

No, you don’t need to compile PHP programs before execution, like C++, because PHP is an interpreted language. This interpretation feature allows you to make changes in the source code and test the changes without compiling the codes into binary forms. This makes for fasterPHP code execution with high-performance outcomes. The in-built memory management feature also helps to negate the impact of the additional runtime load overhead associated with the interpreter.

10. What is the application of the symbol “@” in PHP?

The main application of PHP’s symbol “@” is to suppress the error message. You can utilize this symbol to ignore the expression which usesthis symbol as a prefix. In other words, PHP manages error if it happens in the statement started with @.

11. List top PHP CMS platforms.

A user-friendly CMS platform can help you make excellent and functional websites and web apps. The right CMS plays a critical role in developing applications.

  • WordPress
  • Magento
  • Drupal
  • Joomla
  • Opencart
  • OctoberCMS
  • ExpressionEngine
  • Craft CMS
  • PyroCMS
  • TYPO3

Click here for more info on each CMS platform.

12. Explain different types of PHP variables.

  • Integer: It is a non-decimal signed number(positive or negative).
  • Float (Double): It is a decimal number or exponential number.
  • Boolean: It can be either True or False.
  • String: It is a string of characters.
  • Array: It is a collection of similar types of data stored under a single name.
  • Object: It has methods and data as a single unit called class.
  • NULL: It is a special data type which can store only one value- NULL.
  • Resource: It is a special data type which stores reference to external resources.

13. How does PHP interact with HTML?

The fact is that PHP and HTML can easily interact with each other because PHP can quickly generate HTML, whereas HTML can pass information to PHP. There are many ways through which PHP can interact with HTML. But, you can divide it into two main ways.

The first way is to embed the PHP code in the HTML file itself with the .html extension.
The second way is to merge the PHP and HTML tags in .PHP files.
Both are simple to implement; however you should take note of functions while integrating.

14. What are constructor and destructor in PHP ?

PHP constructor and destructor are special type functions that are automatically called when a PHP class object is created and destroyed.

Generally, Constructor is used to initializing the private variables for class and Destructors to free the resources created /used by the class.

Here is a sample class with a constructor and destructor in PHP.

class Foo {

private $name;
private $link;

public function __construct($name) {
$this->name = $name;

public function setLink(Foo $link){
$this->link = $link;

public function __destruct() {
echo ‘Destroying: ‘. $this->name;

15. How to register a variable in PHP session ?

In PHP 5.3 or below we can register a variable session_register() function.It is deprecated now and we can set directly a value in $_SESSION Global.

Example usage:

// Starting session
// Use of session_register() is deprecated
$username = “PhpScots”;
// Use of $_SESSION is preferred
$_SESSION[“username”] = “PhpScots”;

16. What is default session time and path in PHP. How to change it ?

The default session time in PHP is 1440 seconds (24 minutes) and the Default session storage path is temporary folder/tmp on the server.

You can change default session time by using below code

// server should keep session data
for AT LEAST 1 hour
ini_set(‘session.gc_maxlifetime’, 3600);

// each client should remember their
session id for EXACTLY 1 hour

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