PHP Interview Questions: 20 of the Most Common Ones

If you ever thought about becoming a full-time programmer, now’s your perfect chance - with programming and scripting languages on the rise in popularity, various world-renowned companies are searching for programming and design experts. These companies are usually ready to offer hefty salaries and great working conditions, so it’s no wonder that a lot of people are trying to land the job! With PHP being one of the more popular scripting languages, it’s one of the better options to choose from. However, if you want to land a job as a PHP specialist, you’re going to have to be prepared - this is why in this tutorial, we’ll talk about some of the most popular PHP interview questions.

After we cover the PHP interview questions and answers, we’ll talk about how to utilize PHP practice before a job interview. Then, I’ll give you some general tips and advice on how you can maximize your chances of getting the job.

PHP Interview Questions - Introduction

We’ll start with some of the more basic PHP interview questions so that you could get a feel for what the beginning of the interview should be like. After that, we’ll transition to a bit more advanced PHP questions. All in all, at the end of this tutorial, you should have a better understanding of how the interview should go.

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Question 1: What is PHP?

Probably the very first question that you are likely to get asked during your job interview is “what is PHP?” or “what does PHP stand for?”. Some advice here would be that you should try to answer with as simple of an answer as you can - there’s no need to come off as fancy or a know-it-all. Your potential employers will probably appreciate that you can explain somewhat difficult topics in your own words.

So, what does PHP stand for? Well, the acronym itself is derived from “Personal Home Page” - however, the more scientific answer would probably be “Hypertext Preprocessor”.

PHP is an open-source scripting language. Needless to say, it’s one of the most popular scripting languages in the world - you wouldn’t be reading this tutorial if that wasn't the case.

PHP is most commonly used for web development. The language is loved and appreciated because it can be easily embedded into HTML.

Question 2: What is PHP ‘PEAR’?

The PHP PEAR is an extension of the PHP language itself. The acronym stands for “PHP Extension and Application Repository”.

PEAR is mostly used by experienced programmers - it offers more options and functions than just the standard PHP version.

Question 3: What is PHP used for?

There are quite a few common uses for PHP. Just to name a few:

• It can create, write, close system files.
• It can encrypt data or prevent people from accessing parts of your website.
• It’s used to play around with cookies - you modify and set them according to your needs.

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Question 4: How many supported PHP versions are there?

Currently, there are four versions of PHP - PHP 5.6; PHP 7; PHP 7.1 and PHP 7.2.

It is generally advisable to use the newest (7.2) version.

Question 5: Name the types of errors in PHP.

There are three main types of errors in PHP - notices, warnings, and fatal errors.

Notices are the most commonly encountered errors - they aren’t detrimental to the well-being of your code. Warnings are the tier-two errors, but they’re also non-lethal to the code running process. Fatal errors, however, are a different story - once a fatal error happens, your code running process is immediately terminated.

Some PHP interview questions might require you to go a bit more in-depth with your answers - don’t worry, we’ll reach them in a bit. If you answer the question like in the above-given example, however, you should be good. A nice rule of thumb that you can follow whilst answering PHP questions is to always give a direct answer, but also follow with a 1-2 sentence explanation. That will reveal that you do indeed know what you’re talking about, and make your answers more credible.

Question 6: What is the most common tag to embed PHP into HTML?

The most common tag is:

<?php ……… ?>

Question 7: Is PHP an OOP programming language?

OOP stands for “object-oriented programming”. It is a type of programming language that focuses on the object of the task, with all resources and functions aimed at creating and furthering its development.

PHP 5 is considered to be a great OOP language - it possesses a lot of the features that OOP represents.

Question 8: When would you use the ‘final method’?

The final method is used on a method with a purpose to make it no longer overridable.

Question 9: Is PHP multiple or single inheritance?

This is one of the more fancy-worded PHP interview questions, but don’t let it fool you - the answer is pretty simple.

In PHP, you can only extend a class form another singular class - this means that PHP is of single inheritance.

Question 10: How to enable the use of ‘image’ in PHP?

To use the image function in PHP, you need to have downloaded the GD library - a graphics drawing tool that lets you alter the data information of an image.

So, these were the first 10 PHP interview questions. As I’ve mentioned in the beginning, they aren’t that tough - such PHP questions are designed to check if you even know what you’re talking about, or are you just some random person from the street that decided to apply for a PHP-related job position.

Now, I’ll give some more advanced PHP interview questions - this is the type of questions that you might get asked when the potential employer figures out that you do know a thing or two about PHP. These questions usually require some practical coding action or a more thorough explanation.

Question 11: How would you connect a MySQL database to PHP?

You would do so following the code below:

connection mysql_connect(pepper, Daniel, 12345, Applesauce, client_flag);

Here, “pepper” is the host while “Daniel” is the username and the numbers 1-5 are an example of a password. “Applesauce” is the name of the database that you’re trying to connect to.

Question 12: How many objects can you create in PHP?

Unlimited. However, there’s a catch.

If you want to start creating objects in PHP, you’ll first need to define their class. After that’s done, you can create an unlimited number of objects in that class.

Example:

class Tires
{
}
$car = new Tires();

Question 13: Explain ‘_construct()’ and ‘_destruct()’.

In PHP, objects belonging to classes have inbuilt Construct and Destruct options.

Once you create a new object within a class, the option is automatically enabled within it. This allows the object to copy the parameters and settings of the class and automatically assign them to itself.

On the other hand, if destruct is enabled, it automatically deletes any settings of the new object.

This can be one of the possible PHP interview questions relating to the before-mentioned OOP (object-oriented programming). It can be a great example of how PHP is an OOP language.

Question 14: What’s the difference between ‘==’ and ‘===’?

== (equal) should be used when you want to check if the values of two separate operands are equal to each other or not. === (identical), on the other hand, should be used when you want a super-specific answer - it checks not only the values but also the types of operands.

Question 15: Can you set a maximum execution time within a PHP script?

Yes, yes you can, and there are two ways to do it. But why would you want to do that in the first place?

Sometimes, when you run your code, you might encounter an error that warns you that you exceeded the ‘maximum execution time’ limit. This will prevent your code from running further on, thus failing the process.

To avoid this, you need to implement a command at the very beginning of your code. Another way to do this is to implement the same command in the .ini file.

Question 16: When do you use ‘@’?

The “@” command is used to avoid problems in your code by simply telling PHP to deal with them for you.

What you would do is simply add the “@” command at the beginning of a line with code that might provoke an error message. Once added, “@” will pass any errors that line of code provokes to PHP.

Question 17: How do you find out the length of an array?

To find out the length of an array, you would simply need to utilize this code:

<?php
$array=['php', 'is', 'really', 'cool'];
echo count($array);
?>

The output here is 4.

The sentence “PHP is cool” is made out of 4 words, which is equal to the output. This means that the code worked!

Question 18: How are objects passed in PHP - by reference or by value?

This is yet another one of those PHP interview questions and answers that are closely related to OOP - in PHP, objects can only be passed by value.

Question 19: Compare the ‘include()’ and ‘require()’ functions through how they deal with possible issues within the code.

The include() the command isn’t of the highest priority, so if a code execution fails at the point where include() is located, it will only send out a warning and continue running.

As for require(), it is quite a different story. As the name of the function implies, that portion of the code is required to be able to load the program. If there’s an error where is located, the code will experience a fatal error and crash.

Question 20: How to export PHP data into Excel?

This is one of the more important PHP interview questions, for a lot of companies use Excel as the primary source of data viewing and sharing.

To be able to export PHP data in an Excel sheet, you will have to change the format of the file. Probably one of the most common types of such files would be a .csv formatted file.

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General Tips

Now that we’ve covered some PHP interview questions, you should have a better understanding of what your employers will expect from you as a potential future employee. Needless to say, these questions just scratched the top of the iceberg - there are thousands and thousands of different variations of what you might get asked during your job interview. However, if you remember the ones from this guide, it will already give you a big advantage.

Let’s move on to something that isn’t this technical - some general tips and tricks that you can use to have a better experience before, during and after your job interview.

Sleep

Yes, I know - you’ve heard it all before. Sleep is important for your health, rest is good, yadda yadda… But seriously - think about it.

You can have awesome PHP skills and a great sense of how computers work in general - it won’t matter if you come to the interview looking like you haven’t slept since 2003. Your employers might see that as you not having a strong work ethic and not being able to manage the stuff that you have to do, thus needing to do it late at night. This isn’t the vibe that you want your interviewers to sense, now is it?

Studying

Studying and preparing for the interview is great, but there’s also such a thing as “overthinking”. Remember - the company needs to see your personality just as much as they need to see your knowledge. If you come off as lazy (or on the other side of the spectrum - as a tryhard) they might show you the door fast. What you want to do is find a balance between studying and relaxing.

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Practice

There are a lot of places on the internet that you can utilize for PHP practice. You should look into it - it can be one of the best ways of preparing for the possible PHP interview questions. Check out this guide to learning PHP to find out more about such places.

What you can do is take the PHP interview question and answers from this tutorial and test them “on the field” - actually try your coding with PHP and see if everything works. This will not only enhance your performance but will also grant you a deeper understanding of PHP, which in turn might be the deciding factor during your job interview.

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Conclusions

We have reached the end of this “PHP Interview Questions” tutorial. We’ve talked about what does PHP stand for, I gave you some of the most common PHP interview questions and some general tips on how you can perform better during your job interview and utilize PHP practice while preparing for it.

I hope this information will be useful for you and help you land that dream job!