PHP Interview Questions and Answers

In this collection, I have chosen 50+ mostly asked PHP interview questions and answers, which will surely help you to get success in interviews.


1. What is PHP?
PHP (Hypertext Preprocessor) is a popular open source scripting language used to develop web applications. It is primarily used for server-side scripting, meaning the scripts are executed on the server instead of the user’s computer. PHP is cross-platform and can be used with many different operating systems, such as Windows, Linux, macOS, and Apache.PHP is open source software.


2. What are the main features of PHP?
The main features of PHP are:
• Efficiency – PHP is very efficient, allowing it to process requests very quickly.
• Interpreted – PHP is interpreted, which means that the code doesn’t need to be compiled before being used.
• Open source – PHP is an open source language, meaning that it is free to use and modify.
• Security – PHP has many built-in security features.
• Platform independence – Any platform can support PHP.


3. What are the differences between PHP 4 and PHP 5?
PHP 4 is the older version of the language, while PHP 5 is the current version. The major differences between them are that PHP 4 is interpreted, while PHP 5 is compiled; PHP 4 does not support object-oriented programming, while PHP 5 does; and PHP 5 has a more efficient memory utilization. Additionally, PHP 5 supports advanced features like the SimpleXML library, improved MySQL support, and improved multithreading support.

PHP Interview Questions

4. What is the difference between PHP and HTML?
PHP is a programming language used to create dynamic web pages, while HTML is a markup language used to structure and present content on the web. PHP code can be embedded into HTML documents, and HTML can be used to display the output of PHP scripts.


5. How does PHP compare to other languages?
PHP is a fast and light-weight language, which makes it great for developing web structure. It is also easy to learn and use, and is commonly used with MySQL and other databases. It is well documented and has good online support.


6. What is the purpose of the ‘if’ statement in PHP?
The if statement is used to check for a certain condition and execute code based on the result of that condition. It is used to create conditional statements that will allow for different results depending on certain circumstances.


7. What is the use of the ‘foreach’ loop in PHP?
The foreach loop is used to iterate over an array or a collection of data. It can be used to loop through each element of an array or an object and perform a certain action on each element.


8. What is a session in PHP?
A session in PHP is a way to store data for a particular user over multiple page requests. Each visitor to a website is given a unique session ID, which can be used to store data such as username, shopping cart content, and other information relevant to the user.


9. What is the difference between echo and print in PHP?
echo and print are both used to output data to the user. The main difference between echo and print in PHP is that echo has no return value while print has a return value of 1, so it can be used in expressions. Echo can also take multiple parameters while print can take only one.


10. What is the difference between == and === in PHP?
The ‘==’ operator checks if two values are equal, while the ‘===’ operator also checks the data type of the compared values. The difference is that == checks for value equality while === checks for both value and type equality.


11. What is the difference between include and require in PHP?
Include and require are both used to include files within a PHP script. The difference between the two is that if the file being included cannot be found then include will emit a warning while require will throw a fatal error.


12. What is the difference between GET and POST in PHP?
GET and POST are two methods used to send data to a webserver. The primary difference is that GET data is visible in the URL whereas POST data is not. POST is generally used to send larger amounts of data or modify server-side data, while GET is used to retrieve data.


13. How can we pass variable through the navigation between the PHP pages?
We can pass the variables through the navigation using sessions, cookies or URL parameter.


14. What is difference between Session and Cookie?
The main difference between session and cookie is that cookie are stored on user computer and session are stored on server side.


15. List the looping structures in PHP?
The looping structures in PHP are for, foreach, while and do-while loops.


16. What is the difference between unset and unlink in PHP?
The unset function removes a variable from the currently defined scope while the unlink function deletes a file from a specified path.


17. How can we get the IP address of a user in PHP?
The function ‘$_SERVER[‘REMOTE_ADDR’]’ can be used to get the IP address of a user in PHP.


18. What are the different sorting functions available in PHP?
The different sorting functions available in PHP are sort(), natsort(), asort(), arsort(), ksort(), and usort().


19. What is header() function in PHP?
The header() function in PHP is used to send a raw HTTP header to a client. It is usually used to send a status code, redirects, and other types of information to the browser. It is an important part of the HTTP protocol and is used in almost all web apps to direct data flow.


20. What is PDO?
PDO stands for PHP Data Objects. It is a PHP interface for database access. It allows for more secure and portable code, since it uses a consistent API regardless of the database you are using.


21. What is MVC?
MVC stands for Model-View-Controller and it is an architectural pattern for developing applications. The model represents the data, the view is the user interface, and the controller is responsible for controlling the interaction between the model and view.


22. What is the difference between include and require statements in PHP?
The include and require statements are used to import a specific file into the current PHP code. The difference between the two is that require will cause a fatal error if the file is not found, whereas include will issue a warning but continue executing the script.


23. What is the use of ‘echo’ in PHP?
The echo command is used to output a string of text in the PHP code. It is an alternative to the print command, and it can be used to output the result of a calculation or a variable value.


24. What is the difference between abstract classes and interfaces in PHP?
An abstract class is a class which cannot be instantiated, but can contain both concrete and abstract methods. An interface is a type of class which can only contain abstract methods. An interface must be implemented by a class to become useful.


25. What are the main types of error in PHP?
Four types of errors in PHP are following:
• Notice – these are minor errors, such as a missing parameter.
• Warning – these are more serious errors, such as a missing file.
• Fatal – these are the most serious errors, such as syntax errors.
• Syntax – these are errors related to the syntax of the PHP code.


26. What is the difference between a local and a global variable in PHP?
A local variable is a variable which is declared within a function. A global variable is any variables which are declared outside of a function. Local variables have a limited scope, while global variables can be accessed from anywhere in the code.


27. What is the purpose of the ‘static’ keyword in PHP?
The static keyword is used to define a static variable, which is a variable that retains its value between multiple calls of a function. It can be used to store values between different invocations of a function and allow them to be accessed globally.


28. What is the purpose of the ‘namespace’ keyword in PHP?
The namespace keyword is used to declare a namespace. A namespace is a logical separation of code, allowing you to avoid naming conflicts. You can create a namespace to group related code and refer to it using a shorter and more descriptive name.


29. What is the purpose of the ‘this’ keyword in PHP?
The “this” keyword in PHP is used to refer to the current object instance within a class. It is used within a class or object to refer to itself, rather than a global or static context.


30. What is the purpose of the ‘self’ keyword in PHP?
The ‘self’ keyword is used in PHP to refer to the current class. . It can be used within a class to access static variables and methods, as well as to refer to the class itself.


31. What is the purpose of the ‘__construct’ function in PHP?
The __construct function is the constructor function for a class. This function is called when a class is instantiated, and it can be used to perform any initialization tasks the class may need.


32. What is the purpose of the ‘ternary’ operator in PHP?
The ternary operator is a shorthand notation for if-else statements. It can be used to perform a condition check and evaluate two expressions based on the result of the condition. It is a quick and efficient way to handle simple conditions.


33. How do you define a constant in PHP?
A constant in PHP can be defined using the “define” function.
define(“CONSTANTNAME”, “value”, true);
The third parameter is optional, and should be set to true if the constant should be case sensitive.


34. What are magic methods in PHP?
Magic methods are the special kind of functions in PHP which are identified by a ‘__’ prefix and are triggered on specific events. These events can be anything like object creation, extending a class, modifying certain property, etc. Some of the common magic methods are __construct(), __destruct(), __call(), __get(), __set(), etc.


35. What type of inheritance that PHP supports?
PHP supports only single inheritance. It means that a class can inherit from only one single class.


36. What does the “$” symbol in PHP?
The $ symbol in PHP is used to signify variables. All variables in PHP must start with a $ symbol before their name.


37. How can we connect to a MySQL database from a PHP script?
We can connect to a MySQL database from a PHP script using the MySQLi extension or using the PDO extension (PHP Data Objects).
$mysqli = new mysqli(“localhost”, “username”, “password”, “database”);
$pdo = new PDO(“mysql:host=localhost;dbname=database”, “username”, “password”);


38. What are the parameters and how can we pass them in PHP?
Parameters in PHP are how we pass information or data from the URL in a web browser to the server, which is then used to identify what action to perform or what data to display and send back to the browser. Parameters are sent as name-value pairs and are separated by the “&” character.
Sending parameters to the URL:
Accessing parameters in PHP:
$name = $_GET[‘name’];
$id = $_GET[‘id’];




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