Top 40 PHP Developer Interview Questions and Answers

The demand for PHP developers remains high due to its versatility, flexibility, large codebase, CMS facility, and large community support. With new frameworks, libraries, and best practices, PHP and its ecosystem are always changing. Candidates may find it difficult to stay on top of these changes. Here we have curated top 40 PHP developer interview questions and answers to help you ace the interviews confidently. Check out our PHP course syllabus to get started.

Basic PHP Questions for Interview with Answers

Here are some basic PHP interview questions and answers for freshers:

1. What is PHP?

“Hypertext Preprocessor” is what PHP stands for. The main objective of this popular general-purpose scripting language is server-side web development. PHP code creates dynamic web pages when it is run on the server and placed within HTML.

2. What are PHP’s salient features?

The key features of PHP are as follows:

• Open-source: It is freely accessible and simple to distribute and alter.
• Platform Independence: Compatible with a wide range of operating systems, including Linux, macOS, Windows, and others.
• Huge Community and assistance: A large community offers a variety of libraries, resources, and a great deal of assistance.
• Database Connectivity: Outstanding support for a wide range of databases, including Oracle, PostgreSQL, MySQL, and others.
• Object-Oriented Programming (OOP) Support: Provides support for OOP ideas such as inheritance, polymorphism, classes, and objects.
• Easy to Learn: Relatively easy to learn and understand, especially for beginners with basic programming knowledge.

3. What are the different data types in PHP?

The various data types in PHP are:

• Integer: Represents whole numbers (e.g., 10, -5, 0).
• Float/Double: Represents numbers with decimal points (e.g., 3.14, -2.5).
• String: Represents a sequence of characters (e.g., “Hello”, “PHP”).
• Boolean: Represents a logical value (e.g., TRUE, FALSE).
• Array: An ordered collection of values (can hold multiple data types).
• Object: Represents an instance of a class.
• NULL: Represents the absence of a value.

4. Describe the distinction between == and === in PHP.

== (Loose comparison): Verifies only value equality.

=== (Strict comparison): Verifies that the value and data type are equal.

5. What are variables in PHP?

In a PHP script, variables are used to temporarily store data. A dollar symbol ($) and the variable name are used to declare them.

Example, $name = “John Doe”;

Learn from scratch with our web development training in Chennai.

6. How do you define and call a function in PHP?

Define:

PHP

function myFunction($param1, $param2) {

    // Code to be executed

    return $result; 

}

Call:

PHP

$result = myFunction(“value1”, “value2”); 

7. What are the different ways to include files in PHP?

Here are the various ways to include files in PHP:

• include(): Incorporates the given file. It creates a warning if the file cannot be located.
• include_once(): Prevents duplicate inclusions by including the provided file just once.
• require(): Provides the given file. The script stops running and generates a fatal error if the file cannot be located.
• require_once(): Prevents duplicate inclusions by including the provided file only once. It creates a fatal error if the file cannot be located.

8. What are superglobals in PHP?

No matter the scope, superglobals are built-in variables that are always available.

Examples: $_GET, $_POST, $_REQUEST, $_SERVER, $_SESSION, $_COOKIE, and $_FILES.

9. Explain the difference between $_GET and $_POST in PHP.

$_GET: Data is passed through the URL using $_GET, which is displayed in the address bar of the browser.

$_POST: Data in the HTTP request body (not visible in the URL) is passed via $_POST.

10. What is a session in PHP?

PHP sessions allow for the temporary storage and accessibility of data across all website pages. A temporary file with the values of the different session variables will be created. When you exit the website, this will be lost.

11. How do you handle errors and exceptions in PHP?

Error Handling: To manage which errors are reported, use error_reporting(). Use try…catch blocks to handle errors in a more organized manner.

Exception Handling: To deal with exceptions, use try…catch…finally blocks.

12. What is object-oriented programming (OOP) in PHP?

PHP’s object-oriented programming (OOP) approach structures applications using classes and objects. Because it enables developers to write understandable, maintainable, and reusable code, it is a popular paradigm for PHP.  

13. How does OOP work in PHP?

• Classes: Object templates that combine functions and data
• Objects are instances of a class that carry over its attributes and actions.
• Inheritance: A class can inherit traits, functions, and behaviors from another class through inheritance.
• Polymorphism: Objects of different classes can be regarded as belonging to the same superclass due to polymorphism. 

14. What are the advantages of OOPs in PHP?

The benefits of OOPs in PHP:

Reusable Code: Classes can inherit properties and methods from other classes due to OOP, which encourages code reuse.

Maintainable Code: By enabling objects of diverse classes to be viewed as objects of a shared superclass, OOP encourages maintainable code.

Readable Code: Because OOP structures applications like real-world objects, it makes them easier to read.  

Examples of OOPs in PHP:

• The Animal class is a parent class that has a function ($eat()) and a property ($name).
• The class of dogs: An offspring class derived from the Animal class
• The class of cats: An offspring class derived from the Animal class 

15. Describe PHP’s class and object concepts.

• Class: An object creation blueprint or template. explains methods and properties.
• Object: A class instance. represents a particular entity with data of its own.

Learn from anywhere with our web development online course program.

16. What are the four pillars of OOP?

The four major pillars of OOPs in PHP:

• Abstraction: Disguising the specifics of internal implementation.
• Encapsulation: It is the process of combining methods that work with data (properties) into a single unit (class).
• Inheritance: Creating new classes (child classes) from preexisting ones (parent classes) and passing on attributes and functions is known as inheritance.
• Polymorphism: The ability to treat objects of different classes as though they were of the same type is known as polymorphism.

17. What is a constructor in PHP?

When an object is formed from a PHP class, a particular method called a constructor function is automatically invoked. Its objective is to carry out any necessary setup operations or initialize the object’s properties. The __construct() method in PHP is used to define a constructor function. 

18. What is a destructor in PHP?

When the script is halted or quit, or when an object is destructed, a destructor is invoked. 

PHP will automatically invoke the __destruct() function at the conclusion of the script if you construct one. 

19. What are interfaces in PHP?

Classes must abide by a contract defined by interfaces. They outline a collection of procedures that a class needs to follow.

20. What are namespaces in PHP?

Code can be organized using namespaces, which also help to avoid naming conflicts between classes that share the same name.

Enhance your web design and development skills with our WordPress course in Chennai.

Interview Questions on PHP for Experienced Candidates

Here are the senior PHP developer interview questions:

1. What are cookies in PHP?

A cookie is a little file that the server places on the user’s computer. Every time the same machine uses a browser to request a website, the cookie will be transmitted. PHP cookies can be used to create and retrieve cookie values. Text files known as cookies are stored on the client computer in order to be monitored.

2. What is the difference between cookies and sessions?

Sessions and cookies are both used to store user data on a website, but the main distinction is that sessions store data on the server, with only a session identifier being saved on the user’s browser, whereas cookies are small text files stored on the user’s device. In other words, sessions are server-side storage, while cookies are client-side storage.

3. What is PDO (PHP Data Objects)?

PHP Data Objects, or PDO, is a simple and reliable framework for database access in PHP. Any database driver that implements the PDO interface has the ability to expose database-specific features as standard extension methods.

4. What are prepared statements in PDO?

The ability to efficiently run the same (or comparable) SQL statements repeatedly is known as a prepared statement. In general, prepared statements operate as follows: 

• Get ready: The database receives a template for a SQL statement. 
• Parameters are values that are left undefined and are tagged “?”.

5. What is SQL injection?

A kind of security flaw that lets hackers insert malicious SQL code into database queries in online applications. By inserting malicious SQL queries into an entry field for execution, SQL injection is a code injection technique used in computing to attack data-driven systems. 

Example: to dump the database contents to the attacker.

6. How can you prevent SQL injection in PHP?

To prevent SQL injection in PHP, we can follow the below:

• Make use of prepared statements.
• Verify and clean user input.
• Make use of parameterized queries.
• Use an object-relational mapper, or ORM.

Master in mobile app development with our mobile app development course in Chennai.

7. What is an ORM (Object-Relational Mapper)?

By essentially translating between the data structures used by a relational database and the objects used in their application code, an ORM (Object-Relational Mapper) is a software tool that enables developers to work with a database using object-oriented programming concepts. 

• This eliminates the need to write raw SQL queries directly.
• It automatically maps data between database tables and application objects
• It makes data manipulation easier and development processes more efficient.

8. What are the importances of ORMs?

The key features of ORMs are as follows:

• Bridging the Gap: ORMs serve as a link between the relational database model and the object-oriented paradigm of computer languages.
• Abstraction Layer: This makes code easier to read and maintain by enabling developers to work with database data as though it were a standard application object.
• Automatic SQL Generation: The system automatically creates the INSERT, UPDATE, and DELETE SQL queries required to carry out database operations when a developer works with an object using the ORM.
• Increased Development Speed: ORMs can drastically cut down on development time by managing the intricacies of database interface.  

9. What is JSON (JavaScript Object Notation)?

Data can be stored and sent using the text-based JSON (JavaScript Object Notation) standard. It is a widely used data format in software engineering, data analysis, and web development.

The uses of JSON:

• Web development: Data is transferred between a web application and a server using JSON. For instance, after loading, a web page may ask the server for further information.
• Data analysis: Google’s BigQuery and other data storage systems employ JSON to store and analyze data.
• Software engineering: Data can be shared between platforms and computer languages using JSON.  

10. How do you encode and decode JSON data in PHP?

PHP arrays and JSON data formats are quite similar. Functions for encoding and decoding JSON data are built into PHP. JSON_encode() and JSON_decode() are the relevant functions in question. Only UTF-8 encoded string data can be used with both functions. 

Encoding: json_encode($data).

Decoding: json_decode($json_string).

Enrich your app development skills with our MEAN Stack course in Chennai.

11. Explain AJAX?

Web applications can transmit and receive data in the background due to a group of web development technologies called AJAX (Asynchronous JavaScript and XML). Web apps become more responsive to user input as a result.

Functions of AJAX:

• AJAX retrieves content from the server using asynchronous HTTP queries.
• Without reloading the entire page, the new content is used to update particular sections of the page.
• Because of this, users may interact with web pages without having to constantly reload them.  

Advantages of AJAX:

• AJAX improves the responsiveness of web apps.
• AJAX enables dynamic content changes on web pages.
• One-page apps can be made with AJAX. 

Examples of AJAX:

• Google Maps and Gmail are two instances of AJAX in action: AJAX is used by Google in their online apps.
• Social bookmarking websites: AJAX is used by websites such as Digg and Reddit to handle user votes.  

12. What is a regular expression in PHP?

a pattern for text manipulation and matching. They are effective tools for string validation, replacement, and search.

In other words, a string of characters that specifies a search pattern is called a regular expression, or regex. 

A phone number in the pattern xxx-xxx-xxxx can be matched by the regex /[0-9]{3}-[0-9]{3}-[0-9]{4}/, whereas the regex /[a-z]+/ matches one or more lowercase letters.

13. What is the use of the preg_match() function in PHP?

The function preg_match lets you search a string for a certain pattern using regular expressions. 

The preg_match() function in PHP is used to determine whether a given text fits a defined regular expression pattern. It returns true if a match exists and false otherwise.

• Functions: The string to search within is the second input, and the regular expression pattern is the first.
• Return Value: It returns 0 (false) if no match is discovered, 1 (considered true) if the pattern is found in the string, or false in the event of an error. 

Use Cases of Preg_Match:

• Verifying that user input adheres to a predetermined format (e.g., phone number, email address).
• Using a pattern to extract particular data from a text (like parsing HTML).
• Verifying whether a string contains a specific keyword.

14. What are some common PHP frameworks?

A PHP framework is a platform that gives programmers a collection of resources and tools to help them create web apps more quickly. It offers a framework for managing databases, processing requests, and structuring code.

Some of the common PHP frameworks:

• Laravel.
• Symfony.
• CodeIgniter.
• Zend Framework.
• Yii.

Review your web development skills with our full-stack developer interview questions.

15. What is a composer in PHP?

For the PHP programming language, Composer is an application-level dependency manager that offers a standardized structure for handling PHP software dependencies and necessary libraries. Jordi Boggiano and Nils Adermann created it and are still in charge of it.

16. What is a PSR (PHP Standards Recommendation)?

By defining standards for common aspects of PHP development, such as autoloading, interfaces, and coding style, a PHP Framework Interoperability Group (PHP-FIG) can create a set of guidelines and coding standards known as a PSR (PHP Standards Recommendation). This makes code easier to read and maintain across different frameworks and libraries.  

Important facts regarding PSRs:

• The goal is to standardize PHP code so that developers may work on various projects with ease and using the same coding techniques.
• PHP Framework Interoperability Group (PHP-FIG) is in charge of managing it.  

Examples of PSRs:

• PSR-1: Basic Coding Standard 
• PSR-4: Autoloading Standard 
• PSR-12: Extended Coding Style Guide 

17. What is the difference between echo and print in PHP?

The primary distinction between print and echo in PHP is that print can only output a single string, but echo can output many strings.  

The primary distinction between print and echo in PHP is that print can only output a single string, but echo can output many strings.  

Reshape your career with our full-stack developer course in Chennai.

18. How do you handle time zones in PHP?

The date_default_timezone_get() function in PHP allows you to retrieve the current timezone. The current timezone is represented by the string that this method returns.

19. What is caching in PHP?

Caching enhances performance by storing frequently accessed items in memory. PHP provides a number of caching options, including:

• File caching: Keeping information on the server in files.
• Memcached: A distributed memory object caching solution with excellent performance.
• Redis: An in-memory data store with message broker, database, and cache functions.

20. Describe some security practices in PHP development.

Some of the common security practices in PHP development are:

• Input Validation and Sanitization: To guard against attacks like SQL injection and cross-site scripting (XSS), always validate and sanitize user input.
• Use Prepared Statements: Make Use of Prepared Statements Avoid vulnerabilities caused by SQL injection.
• Securely Manage Session Data: Make use of secure session IDs and guard against manipulation of session data.
• Escape Output: To avoid XSS attacks, escape user-provided data before it is shown on the website.
• Update PHP and Extensions Frequently: To fix security flaws, make sure your PHP installation and extensions are up to date.
• Adopt a Robust Password Policy: Make sure users are required to use strong passwords.

Explore all our software training courses and start your IT career.

Conclusion

Many basic and complex subjects are covered in this extensive collection of 40 PHP developer interview questions and answers. It seeks to improve your fundamental to advanced PHP understanding in order to assist you in effectively preparing for your impending interviews. Secure your career in web development through our PHP course in Chennai.