Top 25+ PHP Interview Questions for Freshers 

Introduction
Are you going to start your career as a PHP developer? Great, you’ve decided to work with a programming language that runs roughly 80% of the world’s top ten websites, including Facebook, WordPress, Wikipedia, Etsy, and Pinterest. 

Interestingly, it is one of the most extensively used server-side languages, and has been for the past 25 years. Despite its long history, demand for PHP has remained high. According to the US Bureau of Labor Statistics, there will be a 15% growth in web development positions, including PHP positions, by 2026. 

That being stated, one of the first steps in landing a job as a PHP developer is to prepare for the interview. To that purpose, we’ve made a list of Top PHP interview questions that hiring managers are likely to ask to assess your knowledge and skills.

Let’s read about it –

• What is PHP?

This PHP interview question tests the candidate’s basic understanding of PHP.

• Answer: PHP stands for Hypertext Preprocessor, which is a server-side scripting language designed for web development. It’s widely used for creating dynamic web pages and can be embedded into HTML.This question tests the candidate’s basic understanding of PHP. 

• What are the differences between PHP and JavaScript?

 This PHP interview question assesses the candidate’s understanding of server-side and client-side scripting languages.

• Answer: PHP is executed on the server, while JavaScript is executed on the client-side (in the user’s web browser). PHP is used for server-side scripting, handling tasks like database operations and file manipulation, while JavaScript is primarily used for client-side interactivity and DOM manipulation. 

1. What are PHP magic methods? Provide examples.

           This question evaluates the candidate’s knowledge of advanced PHP concepts.

• Answer: PHP magic methods are predefined methods in PHP which have special functionality. Examples include __construct() for constructor methods, __get() and __set() for getting and setting inaccessible properties, __toString() for converting an object to a string, etc. 

• Explain the difference between include and require in PHP.

This question tests the candidate’s understanding of file inclusion in PHP and error handling.

• Answer: Both include and require are used to include and evaluate the specified file during script execution. The primary difference is how they handle errors. If the file to be included is not found, include generates a warning and continues execution, while require generates a fatal error and halts the script execution. 

• What is the use of the isset() function in PHP?

        This question assesses the candidate’s knowledge of handling variables in PHP.

• Answer: The isset() function is used to determine if a variable is set and is not NULL. It returns true if the variable exists and has a value other than NULL, false otherwise. 

• What is the difference between sessions and cookies in PHP?

This question evaluates the candidate’s understanding of managing user data in PHP.

• Answer: Sessions and cookies are both used to store user data, but they differ in where the data is stored and how long it persists. Sessions store data on the server and are active until the user closes the browser or the session expires. Cookies store data on the client-side and can persist for a specified duration even after the browser is closed. 

1. Explain the use of the foreach loop in PHP.

This question tests the candidate’s understanding of loop constructs in PHP.

• Answer: The foreach loop is used to iterate over arrays or objects in PHP. It iterates through each key/value pair in an array or each property in an object, executing the specified block of code for each iteration. 

• What is PDO in PHP?

         This question assesses the candidate’s knowledge of database interaction in PHP.

• Answer: PDO (PHP Data Objects) is a PHP extension that provides a consistent interface for accessing databases. It’s used to perform database operations in a secure and efficient manner by supporting various database drivers and providing features like prepared statements and transactions.

• What are namespaces in PHP?

           This question evaluates the candidate’s understanding of organizing code and avoiding naming conflicts in PHP.

• Answer: Namespaces are a way to encapsulate items like classes, functions, and constants under a specific name to avoid naming collisions between different parts of code. They allow developers to organize and manage code more efficiently, especially in larger projects or when integrating third-party libraries.

• What is the use of the mysqli extension in PHP? How does it differ from the mysql extension?

This question assesses the candidate’s knowledge of database connectivity and the differences between PHP database extensions.

• Answer: The mysqli extension (MySQL Improved) is used for interfacing with MySQL databases in PHP. It provides an object-oriented interface as well as support for prepared statements and transactions, making it more secure and efficient compared to the deprecated mysql extension, which is procedural and lacks features like prepared statements.

• 11. What is the purpose of the htmlspecialchars() function in PHP?

This question tests the candidate’s understanding of security measures in PHP, specifically regarding input/output sanitization.

• Answer: The htmlspecialchars() function in PHP is used to convert special characters to their corresponding HTML entities. It helps prevent XSS (Cross-Site Scripting) attacks by escaping characters like <, >, &, etc., making user input safe to output in HTML. 

• 12. Explain the concept of autoloading in PHP.

                     This question evaluates the candidate’s knowledge of PHP autoloaders and their role in class loading and code organization.

• Answer: Autoloading is a mechanism in PHP that automatically includes the necessary class files when a class is instantiated or used for the first time in the code. It eliminates the need for manual require or include statements for each class file, improving code maintainability and reducing redundancy.

1. What is the difference between == and === operators in PHP?

                 This question tests the candidate’s understanding of comparison operators and type coercion in PHP.

• Answer: The == operator in PHP checks for equality of values, while the === operator checks for both equality of values and data types. The === operator performs a strict comparison, meaning it returns true only if both the values and types of the operands are identical. 

• 14. How can you handle errors and exceptions in PHP?

                   This question assesses the candidate’s knowledge of error handling techniques and best practices in PHP.

• Answer: Errors in PHP can be handled using functions like error_reporting() to control which types of errors are reported, set_error_handler() to define custom error handling functions, and trigger_error() to generate user-defined errors. Exceptions, on the other hand, can be caught and handled using try, catch, and finally blocks in combination with throw to explicitly raise exceptions.

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  15. What are traits in PHP? How do they differ from classes and interfaces?
  This question evaluates the candidate’s understanding of code reusability and composition in PHP.
  • Answer: Traits are a mechanism in PHP that allow developers to reuse methods in multiple classes without using inheritance. Unlike classes, traits cannot be instantiated on their own and are intended to be included within classes using the use keyword. Traits provide a way to share methods across different classes, similar to multiple inheritance but without the associated problems.

1. What are some advantages and disadvantages of using PHP?

This question assesses the candidate’s understanding of PHP’s strengths and weaknesses, as well as their ability to evaluate technology choices.

Answer:

• Advantages: PHP is widely supported, easy to learn and use, has a large community, extensive documentation, and is well-suited for web development with features like built-in support for databases and powerful frameworks like Laravel and Symfony.
• Disadvantages: PHP can sometimes suffer from inconsistent function naming and parameter order, lacks some modern language features found in other languages, and can lead to spaghetti code if not properly structured.

1. Explain the concepts of inheritance, encapsulation, and polymorphism in PHP. Provide examples.

This question evaluates the candidate’s understanding of object-oriented programming (OOP) principles in PHP.

• Answer:
  • Inheritance: Inheritance allows a class (subclass) to inherit properties and methods from another class (superclass). For example, a Car class can inherit from a Vehicle class to reuse common functionality like start() and stop() methods.
  • Encapsulation: Encapsulation is the bundling of data (properties) and methods (functions) that operate on the data into a single unit (class). It hides the internal state of an object from the outside world and only exposes the necessary functionalities through methods. For example, a User class encapsulates properties like name, email, and methods like login(), logout().
  • Polymorphism: Polymorphism allows objects of different classes to be treated as objects of a common superclass. It enables methods to be called on objects without knowing their specific type. For example, a Shape superclass with subclasses like Circle and Square can have a calculateArea() method, which can be called on any object of the Shape hierarchy.

1. What is Composer in PHP? How do you use it in a project?

• Significance: This question assesses the candidate’s knowledge of dependency management and package installation in PHP projects.

Answer:

• Composer is a dependency management tool for PHP that simplifies the process of installing and managing external libraries and packages in PHP projects. It uses a composer.json file to define project dependencies and version constraints.
• To use Composer in a project, you need to install Composer globally on your system and create a composer.json file in the root directory of your project. Then, define the required dependencies in the composer.json file using the require key. Finally, run composer install to install the dependencies listed in the composer.json file.
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1. Explain the concept of middleware in the context of PHP frameworks.

This question evaluates the candidate’s understanding of middleware and its role in web application development using PHP frameworks.

Answer:

• Middleware is a mechanism used in PHP frameworks like Laravel and Symfony to filter HTTP requests and responses before and after they reach the application’s route handlers. Middleware can perform tasks like authentication, logging, session management, CSRF protection, etc.
• Middleware functions are executed in a pipeline, where each middleware component can modify the request or response and pass it to the next middleware in the pipeline. Middleware provides a flexible way to modularize and reuse HTTP request/response processing logic across different routes in an application.

1. What are traits conflicts in PHP and how can they be resolved?

This question assesses the candidate’s understanding of trait composition and conflict resolution in PHP.

Answer:

• Traits conflicts occur when multiple traits used by a class define methods with the same name. PHP doesn’t automatically resolve these conflicts, and it’s the developer’s responsibility to resolve them explicitly.
• Conflicts can be resolved by aliasing conflicting methods using the as keyword to give them unique names, or by explicitly excluding methods from one or more traits using the insteadof keyword. This allows the developer to selectively choose which method implementation to use in the class.

1. What are traits conflicts in PHP and how can they be resolved?

This question assesses the candidate’s understanding of trait composition and conflict resolution in PHP.

• Answer: Traits conflicts occur when multiple traits used by a class define methods with the same name. PHP doesn’t automatically resolve these conflicts, and it’s the developer’s responsibility to resolve them explicitly. Conflicts can be resolved by aliasing conflicting methods using the as keyword to give them unique names, or by explicitly excluding methods from one or more traits using the insteadof keyword. This allows the developer to selectively choose which method implementation to use in the class.

1. Explain the concept of PSR standards in PHP development.

This question evaluates the candidate’s awareness of coding standards and best practices in the PHP community.

• Answer: PSR stands for PHP Standards Recommendations, which are a set of standards and recommendations issued by the PHP Framework Interop Group (PHP-FIG) to promote interoperability and consistency across PHP projects. PSR standards cover various aspects of PHP development, including coding style, autoloading, HTTP message interfaces, and logging. Adhering to PSR standards helps improve code readability, maintainability, and collaboration among developers working on different PHP projects.

1. How does PHP handle sessions? Explain the session lifecycle.

This question assesses the candidate’s understanding of session management in PHP web applications.

• Answer: PHP uses sessions to store user-specific data across multiple HTTP requests. When a session is started, PHP generates a unique session ID for the user and stores session data on the server or in a specified storage mechanism (e.g., files, database). The session ID is typically passed to the client via a cookie or URL parameter. During subsequent requests, PHP retrieves the session data based on the session ID, allowing the application to maintain user state. The session lifecycle includes session initialization, data manipulation, and session termination (e.g., logout, session expiration).

1. What is PHP’s SPL (Standard PHP Library), and why is it useful?

This question evaluates the candidate’s knowledge of PHP’s built-in libraries and their utility in development.

• Answer: PHP’s SPL (Standard PHP Library) is a collection of classes and interfaces that provide a set of standard data structures, iterators, and utilities for common programming tasks. SPL includes classes like SplStack, SplQueue, SplHeap for data structures, and interfaces like Iterator, Countable for iterator manipulation. SPL enhances code reusability, promotes best practices, and improves performance by providing efficient implementations of commonly used data structures and algorithms.

1. Explain the concept of dependency injection in PHP.

This question assesses the candidate’s understanding of software design patterns and dependency management techniques in PHP.

• Answer: Dependency injection is a design pattern in which objects are passed their dependencies (i.e., other objects or values) rather than creating or managing them internally. This promotes loose coupling between classes and makes code more modular, testable, and maintainable. In PHP, dependency injection can be achieved through constructor injection, setter injection, or interface injection, where dependencies are provided to a class either through constructor parameters, setter methods, or interface implementations, respectively.

Conclusion,

Mastering PHP is not just about understanding its syntax and basic concepts but also about being able to apply that knowledge effectively in real-world scenarios. By thoroughly reviewing and understanding the top 25 PHP interview questions outlined in this guide, you’ll not only boost your confidence but also demonstrate your proficiency in PHP to potential employers.

Remember, preparation is key when it comes to job interviews, and by investing the time to study and practice these questions, you’ll be better equipped to tackle any challenge that comes your way during the interview process. Whether you’re a seasoned PHP developer looking for new opportunities or just starting your journey in the world of web development, these interview questions serve as a valuable resource to help you stand out from the competition and land your dream job.