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30+ PHP Interview Questions And Answers

PHP is a widely-used open-source scripting language that is especially suited for web development and can be embedded into HTML. The language is simple for newcomers, yet offers many advanced features for professional programmers. Below are some PHP interview questions that focus on both foundational knowledge for beginners and complex concepts for advanced developers.


Most asked PHP interview questions



What does PHP stand for?

PHP stands for PHP: Hypertext Preprocessor.


How do you declare a variable in PHP?

You declare a variable in PHP with a dollar sign followed by the name of the variable.

$variableName = 'value';


What is the difference between 'echo' and 'print' in PHP?

echo can output one or more strings, while print can only output one string and always returns 1.


Can you explain what a session is in PHP?

A session in PHP is a way to store variables to be used across multiple pages.


What does the 'include()' function do in PHP?

The include() function takes all the text in a specified file and copies it into the file that uses the include function.


How do you create a constant in PHP?

You use the define() function to create a constant in PHP.

define('CONSTANT_NAME', 'Value');


What is the difference between 'GET' and 'POST' methods in form submission?

GET method appends data to the URL and has limits on data length. POST method doesn't display data and can handle large amounts of data.


How do you handle errors in PHP?

PHP has several functions to handle errors, including custom error handlers using set_error_handler() function.


Explain what an array is in PHP.

An array in PHP is a data structure that stores multiple values in a single variable.


What is the purpose of 'isset()' function in PHP?

The isset() function checks if a variable is set and is not NULL.


What are loops in PHP and name the different types?

Loops in PHP are used to execute the same block of code a specified number of times. PHP supports for, while, and foreach loops.


What is a 'function' in PHP?

A function in PHP is a block of code that can be repeatedly called to perform a specific task.


How can you send data from PHP to JavaScript?

You can print data in PHP within a [removed] tag as a JavaScript variable or use AJAX to pass data.


What is an associative array in PHP?

An associative array allows using named keys to identify values.


Give an example of using a variable within a string in PHP.

In PHP, you can include a variable directly in a double-quoted string.

$variable = 'world';
echo "Hello, $variable!";

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What are the main error types in PHP?

The main error types are notices, warnings, errors, and core errors.


Explain the difference between 'require' and 'include'.

require will produce a fatal error and stop the script if the file cannot be included. include will only produce a warning and the script will continue.


How do you prevent SQL injection in PHP?

Use prepared statements with PDO or mysqli and parameterized queries to prevent SQL injection.


Explain the use of 'namespaces' in PHP.

Namespaces are used to avoid name conflicts and to create more readable and manageable code.


How can you increase the execution time of a PHP script?

You can increase the execution time by changing the max_execution_time value in the php.ini file or by calling set_time_limit() in a script.


What's the difference between '=='' and '===' operators?

'==' compares two values for equality after type juggling. '===' compares both value and type.


Explain what 'traits' are in PHP.

Traits allow for code reuse in single inheritance languages like PHP. They are similar to a class, but cannot be instantiated on their own.


What is 'late static binding' in PHP?

Late static binding allows for referencing the called class in a context of static inheritance.


How can you declare an abstract class or method in PHP?

Use the abstract keyword before the class or method declaration.


How does 'bindParam' differ from 'bindValue'?

bindParam binds a parameter to a variable reference. bindValue binds a value to a parameter.


Explain closures in PHP.

Closures are anonymous functions that can access variables outside of their own scope if those are passed to it explicitly.


Explain what a 'static' method is.

A static method can be called without creating an instance of a class.


What is the purpose of the final keyword in PHP?

The final keyword prevents child classes from overriding a method or a class from being inherited.


Explain the concept of 'instanceof' in PHP.

The instanceof keyword is used to determine whether a PHP variable is an instantiated object of a certain class.


Guess what does this PHP code do.

array_walk_recursive($array, function (&$v, $k) {
$v = htmlspecialchars($v);

This code applies htmlspecialchars() to every value of a multi-dimensional array to prevent XSS attacks.


PHP Interview Tips

Understanding the Job Role

  • Before going into a PHP interview, it's crucial that you understand the job description and the skills it requires. Consider studying the company's tech stack and the projects they work on. This will allow you to give more precise answers and demonstrate your suitability for the role. Tailor your responses to show that your expertise solves the company's specific problems. Bring in examples from past projects where your PHP skills made a significant contribution.

Revising PHP Fundamentals and Latest Trends

  • It's essential to have a firm grasp on both basic and complex PHP concepts. Brush up on your knowledge of PHP arrays, loops, functions, error handling, and object-oriented programming. Also, stay informed about the latest PHP trends and updates, such as new frameworks or versions of the language. Knowing these details can showcase your commitment to continuous learning and keeping your skills up-to-date.

Practice Problem-Solving and Code Writing

  • Many interviews include live coding challenges or problem-solving questions. Practice writing clean, efficient PHP code that you can explain to an interviewer. Utilize online coding platforms to sharpen your problem-solving abilities in context with PHP. Being able to write code on the spot confidently can be a determining factor in your performance.

Prepare for Behavioral Questions

  • Technical prowess alone isn't enough; companies also look for candidates who fit well into their team and culture. Prepare for questions about your experiences working as part of a team, managing tight deadlines, and how you've handled past conflicts or challenges. Use the STAR technique (Situation, Task, Action, Result) to structure your responses in a meaningful way.

Follow-Up and Ask Questions

  • Interviewers appreciate candidates who show initiative and genuine interest in the role and the company. Prepare thoughtful questions to ask your interviewers about the job, the team, or the company's future plans. Inquiring about challenges faced by the team or ongoing projects can open a dialogue that lets you illustrate how your skills would add value. After the interview, send a thank-you note to express your continued interest and reiterate how you could contribute to the company.


How much does PHP development cost?

The costs for PHP development can vary based on project complexity and the developer's expertise. With FireHire, rates start at $45/hour. Read more: How much does PHP development cost?

How much does a PHP developer charge per hour?

PHP developer hourly rates are subject to factors like experience, location, and scope of work, usually ranging from $45 to $150. Read more: How much does a PHP developer charge per hour?

How to hire best PHP developers?

Hiring the best PHP developers involves understanding your project's requirements, looking for relevant experience, scrutinizing their problem-solving skills, and leveraging reliable platforms such as FireHire. Read more: How to hire best PHP developers?

Why using FireHire for hiring PHP developers is the best choice?

FireHire offers pre-vetted PHP talent, a quick time-to-candidate, risk-free trial periods, and an expansive network of developers, ensuring you hire not just a developer, but the right developer.

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In the dynamic digital world, PHP back-end development serves as the backbone for creating functional, scalable, and secure web applications. By hiring expert PHP developers, you can leverage their technical execution, cost-effective development tactics, and holistic understanding of API integrations to elevate your digital presence. Whether you need full-time expertise or project-based support, our flexible hiring models are geared to meet your strategic objectives with precision.


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