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In the dynamic world of web development, Hypertext Preprocessor (PHP) stands out as a powerful server-side scripting language. It is renowned for its efficiency in building dynamic websites and mobile APIs. With its extensive database support — including MySQL, Oracle, and PostgreSQL — PHP seamlessly integrates into HTML. This enables developers to manage dynamic content, session tracking, and even construct comprehensive e-commerce sites.
PHP is cost-effective and offers widespread server support, so it has become a pivotal skill in the industry. Because tech companies globally seek proficient PHP developers, understanding the core of PHP is crucial. This article discusses the top 10 PHP interview questions, offering insights to freshers and experienced professionals.
PHP is a versatile scripting language for developing dynamic and interactive websites. It's popular for its ability to embed directly into HTML. This streamlines the process of enhancing web pages with additional functionalities without relying on external files.
Here's a quick overview of what PHP is commonly used for:
Access control to make sure only authorized users can view sensitive information
Cookie management to easily access, set, and manage cookies, which are crucial for tracking user sessions and preferences
Database operations become smoother with PHP interfaces
Form and file handling to handle various tasks, from data submission and retrieval to file uploads and downloads
Email integration into websites, enabling the automated sending and receiving of emails through your web applications
PHP offers a range of system-level functions, such as opening, reading, and writing files, which are essential for robust web application development
Echo can show several strings simultaneously, separated by commas, while print is limited to one string per command. Echo works faster and more efficiently than print, which is relatively slower.
Syntax for 'echo':void echo ( string $arg1 [, string $... ] )For example:
echo "1st”, "2nd”, "3rd”, "Argument”, "Multiple Arguments";
Syntax for 'print':int print ( string $arg)For example:
print "Single Argument";
In PHP, you can work with the following types of variables:
String
Integer
Float (also known as Double)
Booleans
NULL
Resources
Object
In PHP, errors are categorized into notices, warnings, and fatal errors. Notices are minor, non-critical errors that aren't shown to users. Warnings, more significant yet not script-ending, are typically displayed to the user by default. Fatal errors are the most severe, often leading to the immediate cessation of the script.
PHP shows partial case sensitivity. While constructs, function names, and class names in PHP are not case-sensitive, variable names are case-sensitive.For instance, in PHP, you can define user-defined functions in uppercase and then reference them in lowercase without any issues; they will still work correctly.
PEAR stands for "PHP Extension and Application Repository." It serves as a framework and distribution system for reusable PHP components. It enhances PHP, offering advanced programming capabilities to web developers. PEAR has three classes: PEAR Core Components, PEAR Packages, and PECL Packages. It offers a wide range of PHP code snippets and libraries, along with a command-line interface for a smooth package installation.
In PHP, '$this' is a reserved keyword referencing the object that invokes a method. Mostly, it points to the object owning the method, but it can also refer to a different object if the method is called statically from another object's context. The '$this' keyword is exclusively relevant to methods within a class.
A PHP session enables the webserver to track information such as when you began using a website, your activities on the site, and when you exited the site. This tracking is necessary because, unlike personal computers or mobile devices, the web server does not have inherent user knowledge.
Traits in PHP serve as a tool for reusing code in languages with single inheritance. They help overcome some restrictions of single inheritance, so that you can apply the same methods across various independent classes within different class hierarchies.
PHP works with three types of arrays:
Indexed Arrays: These are arrays with numerical indexes.
Associative Arrays: Associative arrays, unlike traditional arrays that store elements in a strict linear index order, use named keys to store element values, allowing for more flexible data organization.
Multidimensional Arrays: These consist of arrays that contain one or more other arrays.
Security is one of the most common (and important) topics in PHP interviews. Be prepared to discuss the fundamentals:
Password hashing: Always use password_hash() and password_verify() instead of outdated hashing methods.
Prepared statements: Use PDO with prepared statements to prevent SQL injection.
Session security: Regenerate session IDs (session_regenerate_id()) and use secure cookies with SameSite attributes.
Input validation: Never trust user input — sanitize and validate everything.
Expect interviewers to probe how you’d secure a login system or prevent common vulnerabilities.
Modern PHP development emphasizes automated testing and code quality. Even if you’re applying for a junior role, having a basic understanding of testing tools can set you apart.
PHPUnit / Pest: Standard testing frameworks for unit and integration tests.
Static analysis: Tools like PHPStan or Psalm detect bugs before runtime.
Code style enforcement: Tools like PHPCS (PHP CodeSniffer) help maintain consistent formatting.
Being able to explain how you’d write a test or integrate static analysis into a CI/CD pipeline is a big plus in technical interviews.
Employers want developers who keep their environments secure and up to date. Show that you understand PHP’s release cycle and support timelines.
As of 2026:
PHP 8.4 – Active release, widely adopted.
PHP 8.3 – Supported but nearing the end of active support.
PHP 7.x – Officially end-of-life (EOL) and should not be used in production.
A quick note in an interview that you follow release notes and update projects accordingly signals maturity and professionalism.
Beyond the basics, mid- and senior-level interviews may include deeper PHP questions. Even if you’re a beginner, being familiar with these concepts can help you stand out:
Generators: Efficiently handle large datasets with lazy iteration.
SPL (Standard PHP Library): Built-in iterators, data structures, and exceptions.
Fibers: Lightweight concurrency introduced in PHP 8.1 for async-like workflows.
OPcache and PHP-FPM: Performance tuning essentials.
These topics demonstrate that you understand how PHP works under the hood — not just how to write code.
To wrap it all up, we've journeyed through the essential aspects of PHP — its practical applications, distinguishing features, and advanced functionalities. This exploration offers a solid foundation for both newcomers and seasoned professionals gearing up for PHP interviews. We've highlighted the language's versatility and critical role in modern web development. Remember, mastering these key PHP concepts is not just about passing interviews — it's about excelling in a field that constantly evolves and innovates.
Step up your web development game with our ‘Web Development with PHP’ skill path. You'll understand everything from PHP basics to advanced concepts, and even learn how to integrate PHP with MySQL. It's a great chance to enhance your skills, build a solid PHP foundation, and stand out in your next web project or job interview.
