Hottest PHP interview questions and their answers

You have finally got a technical interview call for the post that involves PHP skill, But you want to know what kind of questions are mostly asked in such interview than you must have to read this blog CAREFULLY and I am sure you will pass this interview quite easily!

Following are the most hottest interview questions and their answers for PHP.

What is PHP?

PHP is a scripting language used for making dynamic web applications.

Any difference between PHP 7 and PHP 5.6?

PHP 7 allow to declare the return data type of method return value. Following function will return boolean:

public function returnBool(): bool

{  // code  }

All the mysql.* methods have obsoleted in PHP 7

PHP supports multiple inheritance or not?

No, PHP does not support multiple inheritance. It only uses single inheritance that means each child class will have single parent class.

What is final class in PHP?

Class that can not be extended is final class. This is achieved with the help keyword “Final” with class name.

What is final method in PHP?

The method which can not be overridden is final method. This is also achieved with the keyword “Final”

Difference between require() method and include() method?

require() method causes fatal error if file path is invalid while include() method just throws a warning

Difference between require() method and require_once() method?

Both of them perform same task except require_once() checks if file is already fetched or not and than performs next task.

Difference between include() method and include_once() method?

Both of them perform same task except include_once() checks if file is already included or not and than performs next task.

How can you export data to CSV format in PHP?

We have to use file reading and writing functions of PHP to generate and export data into comma separated values format.

What is difference between unlink() method and unset() method?

unlink() method is used to delete a file from file location while unset() method makes a variable undefined.

What are magic functions?

Methods like constructor and destructor are called magic functions.

What is ternary condition?

This is the short form of if else condition. It is used in PHP like:

Condition ? if true : if false

Define session and how to initialize session in PHP?

Session is a logical object to preserve temporary data across multiple web pages. Method of session_start() is used to initialize session in PHP.

session_unregister() vs session_unset()?

session_unregister() method removes a global variable from current session while session_unset() method makes all session variables undefined.

What are types of errors in PHP?


Notices are non-critical errors and do not cause any harm to programs


Serious errors that need to be resolved or else they might cause some issues

Fatal Errors:

The most critical errors that causes the program to terminate.

What is default session time in PHP?

Session expires by default once browser is closed.

Can a class work without constructor?

If you will not write constructor method than PHP will generate and execute a default constructor.

How to check if number is even or odd without any built in methods?

function isEven($number){

        $isEven = true;


                $isEven = !$isEven;

        return $isEven;


$number = 101;

$is = isEven($number) ? “True” : “False”

echo $is;

What is an abstract class?

An abstract class is a class that contains at least one abstract method, which is a method without any actual code in it, just the name and the parameters, and that has been marked as "abstract".

What is interface in PHP?

Interface is used to specify the public methods that a class must implement.

Difference between interface and abstract class?

Any class that implements interface commits to implementing all methods defined in interface while abstract class does not follow this rule.

What is trait?

Trait is used for code reuse in single inheritance language like PHP. We create a trait and then “use” it in our class

What is API?

Application Programming Interface is set of clearly defined methods of communication among various components/apps. API is kind of connection between your live server resources and application.

Difference between RESTful and SOAP APIs?

RESTful API returns response in JSON format while SOAP API returns response in XML.

What is database and how does PHP interact with it?

Database is a collection of related data that is organized so that it can be accessed, managed and updated. PHP mostly works with MySQL database and developers can easily connect with db and interact with it using MySQL methods.

What are table joins and their types?

If data from two or more tables is required than we can join the tables using JOIN query. There are 4 basic types of joins.

  1. Inner Join
  2. Left Join
  3. Right Join
  4. Full Outer Join

Why do we have to use joins?

Sometimes we nee to use data from more than one table in single query and for this purpose joins are used.

What is primary key and unique key?

Primary key is mostly used in table to make whole record unique. It can not be null and has to be distinct. Unique key defines that single column can not have two or more same values.

What is normalization?

Normalization of data is defined as techniques to make db organized with no data redundancy.

Bonus Question:

Swap two numbers using only 2 variables?

$a = 1;

$b = 2;

$b = $a + $b;

$a = $b - $a;

$b = $b - $a;


Topics that you can cover as a whole for web developer interview include Programming Fundamentals, OOP, Database Management and Data Structures

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