Expert PHP Interview Questions for Senior Developer Assessment
Hiring & recruiting developers

In-Depth PHP Interview Questions for Vetting Senior Developers

Ihor Shcherbinin
VP of Recruiting at DistantJob - - - 3 min. to read

Hiring great PHP developers isn’t just about finding someone good with the PHP coding language. It’s really about asking the right, tough PHP questions during interviews. This way, you make sure you’re picking someone who’s not only skilled but also great at solving problems and thinking on their feet.

Here are a few advice and interview questions from my experience as a recruiter to help you hire the right candidate for your project.

How Do I Prepare For Interviewing a Senior PHP Developer? 

PHP developers work back-end components, connecting your application with a database and the client. They are responsible for the server-side web application logic, supporting front-end developers in integrating their work within the application. Keep in mind that this type of role requires teamwork and communications skills. 

Before starting your application and interview process, arrange a meeting with your development team. If you are hiring to replace an existing position, then you can ask who is leaving to create a list of priorities for the project and a range of questions to test the candidate’s skills based on your exact needs. In addition, your existing team can produce different tests for candidates to examine how they deal with tight deadlines, creativity in solving problems, and ability to write complex scripts. 

If you prepare PHP interview questions and tests with your team, it will be easier to spot the most skilled candidate and the right personality for your team. 

Questions You Should Ask During a PHP Interview

Asking advanced PHP interview questions is never an easy task. Here are some samples to guide you in the structure of the interview process. First, get information about the candidate’s background and personality. This initial stage is the moment to analyze characters and their interest in your company. Secondly, ask behavioral questions to understand how the person would work daily with the client. Thirdly, ask questions related to possible scenarios working on your project. Here is when your existing team can isolate specific bottlenecks or methods to ask related to the particular needs of your project. Finally, you can ask role-specific questions to test coding and technical skills. For a full guide on how to hire a PHP developer, make sure to check this article. 

Experience and Personal Background Questions

  1. Tell us about your background and why you decided to apply for this position. 
  2. Our company works in with X products/services. What do you like about the industry? Do you already have experience in it?
  3. How do you think your PHP skills can be helpful in this context?
  4. Why do you want to work on this project specifically?
  5. How would you apply what you know to improve our performance?

With these questions, you don’t only want to test technical skills. Asking about personal background and motivation, you have an overview of the candidates’ personalities. You can find out why they want to work on your project, and which aspect of their personality can concretely support your team. For example, if you know your team is very efficient but struggle in socializing, you can focus on those candidates who are particularly enthusiastic. Or, if you need problem-solving skills, you can test candidates’ creativity to spice up your team’s solution. In a way, there are no right or wrong answers. But there are answers that respond to your needs, so look out for them! 

Behavioral Questions

  1. How do you handle communication with the rest of the team working remotely?
  2. What do you do when you don’t like your colleague’s work but have an important project to finish?
  3. What do you do to prepare for a presentation with clients and investors?
  4. Describe a situation where you had to discuss with a client to propose a better idea. How did you handle the disagreement and convinced the client to chose your solution?
  5. What do you do when you don’t agree with your manager? 

With these questions in mind, you want to picture an ordinary working day of the candidate with your team. Speaking the same language doesn’t mean that people will work well together. Or that a candidate can professionally present your process to clients. The right developer needs to fit in your development process, not only by writing PHP scripts. So, when candidates give their answers, value who has a predisposition to learn faster how your teamwork and speed up the onboarding process.  

Operational and Situational Questions

1. What are the steps to create a new database using MySQL and PHP to store and retrieve user messages for an internet forum?

There are four basic steps to create a new MySQL database in PHP:

  • First, a connection is established to the MySQL server using the PHP script.
  • Second, the connection is validated. If the connection is successful, then you can write a sample query to verify.
  • Queries creating the database are input that later you will store into a string variable.
  • Then, you execute the created queries one after the other.

With this method, you can retrieve and store users’ messages with PHP and MySQL.

2. What is the main difference between asp net and PHP, and why would you choose PHP to create a web design?

PHP is a programming language whereas ASP.NET is a programming framework. Websites developed by ASP.NET may use C#, and other languages such as J#. ASP.NET interprets PHP. ASP.NET is designed for Windows machines, while PHP is a free platform running on Linux servers.

I would opt for PHP scripts because they allow me to edit the design of the whole website without uploading each web page. In addition, with a PHP script, I can access the existing database to retrieve the database and recreate the website.

3. What is the difference between $message and $$message in PHP?

They are both variables. But $message is a variable with a fixed name. $$message is a variable whose name is stored in $message. For example, if $message contains “var”, $$message is the same as $var.

4. What is GET and POST method in PHP and their differences?

The GET method sends the encoded user information appended to the page request. The page and the encoded information are separated by the ? character.

For example:

<a href=""></a>

The POST method transfers information via HTTP headers. The information is encoded as described in the case of GET method and put into a header called QUERY_STRING.

php interview questions

5. How can we increase the execution time of a PHP script for a Digital Ad banner?

The default time for a PHP script is 30 seconds, as you can see in the php.ini file. The function is the set_time_limit(int sec). If the value passed is ‘0’, it takes unlimited time. To clarify, if the default timer is set to 30 seconds and 20 seconds is specified in set_time_limit(), the script will run for 45 seconds.

This time can be increased by modifying max_execution_time in seconds. The time must be changed keeping the environment of the server. This is because modifying the execution time will affect all the sites hosted by the server.

The script execution time can be increased by:

  • Using the sleep() function in the PHP script
  • Using the set_time_limit() function

The default limit is 30 seconds. The time limit can be set to zero to impose no time limit. In this way, PHP script can faster retrieve a digital banner from the database. It can select a random banner from its table records to send it back to the calling script to monitor banner views and clicks from the website.

Role-Specific Questions

1. Explain soundex() and metaphone().

The soundex() function calculates the soundex key of a string. A soundex key is a 4-character long alphanumeric string that represents the English pronunciation of a word. The soundex() function can be used for spelling applications.

The metaphone() function calculates the metaphone key of a string. A metaphone key represents how a string sounds if it is pronounced by an English (native) person. This function can also be used for spelling applications.

echo metaphone("world");

2. What is the use of callback in PHP?

PHP callback are functions that may be called dynamically by PHP. They are used by native functions such as array_map, usort, preg_replace_callback, etc. A callback function is a function that you create yourself, then pass to another function as an argument. Once it has access to your callback function, the receiving function can then call it whenever it needs to.

Here is a basic example of callback function:


function thisFuncTakesACallback($callbackFunc)
    echo "I'm going to call $callbackFunc!\n";

function thisFuncGetsCalled()
    echo "I'm a callback function!\n";



3. What is the use of session and cookies in PHP?

A session is a global variable stored on the server. Each session is assigned a unique id which is used to retrieve stored values. Sessions have the capacity to store relatively large data compared to cookies. The session values are automatically deleted when the browser is closed.

Following example shows how to create a cookie in PHP:

$cookie_value = "edureka";
setcookie("edureka", $cookie_value, time() + 3600, "/your_usename/", "", 1, 1);

if (isset($_COOKIE['cookie'])) {
    echo $_COOKIE["edureka"];

Following example shows how to start a session in PHP:

if (isset($_SESSION['counter'])) {
    $_SESSION['counter'] += 1;
} else {
    $_SESSION['counter'] = 1;
$msg = "You have visited this page " . $_SESSION['counter'];
$msg .= " in this session.";

4. Explain how to submit a form without a submit button.

You can post or submit a form without the button in the following ways:

  • On the OnClick event of a label in the form, a JavaScript function can be called to submit the form.

Example: document.form_name.submit()

  • Using a Hyperlink: On clicking the link, a JavaScript function can be called.


Q5 php IQA code

  • You can submit a form without the submit button in the following:
    • Clicking a link or selecting an option from the drop-down box with the invocation of an onChange event
    • Using JavaScript: document.form.submit();
    • With the header(“location:page.php”);
5. How can we encrypt a password using PHP?

You can use the crypt () function to create one-way encryption. It takes one input string and one optional parameter. You define the function like this:

crypt (input_string, salt)

where input_string consists of the string that you need to encrypt. Salt is an optional parameter. PHP uses DES for encryption. The format is:

php code

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Hire The Best PHP Developer With Us! 

To recap, when preparing advanced PHP interview questions, the first thing to do is to separate the type of questions and understand personality and level of expertise. Based on our experience, the best way to ask the right interview questions is to study your team’s processes and create advanced PHP questions based on that. 

The most important part of your job is to talk with your team and isolate the range of skills you specifically need for your project and the type of personality that suits other members. And for what concerns the hiring process, we are here to help you! During our 10 years of experience, we interviewed hundreds of developers and engineers. From Python to PHP, we can help you make the best technical questions and leave you time to focus on the candidate you want. 

Just contact us! 

Ihor Shcherbinin

Ihor, is the VP of Recruiting at DistantJob. He specializes in sourcing and placing top remote developers for North American companies. His expertise covers the entire recruiting cycle, from pinpointing job needs to finalizing hires. Known for his skill in remote staffing solutions and offshore team integration, Ihor excels in matching the best tech talents with U.S. organizations. His approach to virtual developer hiring is marked by insightful candidate selection and strategic offer negotiation, ensuring the right fit for every role.

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