15 PHP Interview Questions and Answers

Are you looking forward to a PHP interview for a web developing career? Interviews can be very intimidating if you don’t know what to expect. Therefore, we have consolidated some of the top PHP questions interviewers usually ask their clients. In this article, you will get 15 PHP interview questions that will equip you with the confidence to tackle your oncoming PHP interview. The PHP programming language is quite simple yet very fundamental in the generation of cutting edge web pages.

Question 1: What is PHP?

PHP is a server-side scripting language with many frameworks as well as content management systems used in the dynamic creation of web pages. The initials in that word mean Hypertext Pre-Processor. It can be embedded in HTML to manage dynamic web content, databases, session tracking and web design.

Question 2: Which are some common uses of PHP?

As a scripting language, PHP has found application in a variety of sectors discussed below:

  • It executes system functions such as the creation, opening, reading, writing, and closing of files.
  • It plays a role in the managing of forms.
  • PHP can be used in the modification, input and output of elements in a database.
  • It provides an avenue through which cookies variables can be accessed and set.
  • PHP can be used to enforce access integrity on websites.
  • It has data encryption capabilities.

Question 3: How can one embed a PHP code in HTML?

That can be done by making sure that the PHP code is enclosed within the three special markup tags recognized by the PHP parser:


// your php code goes here


Question 4: What is meant by PHP being whitespace insensitive?

In programming, whitespace is defined as the characters that are typed but aren’t visible on the screen such as the spaces, tabs, and end-of-line characters. PHP usually regard these whitespace characters as the same such that it won’t matter how many of them are present in a row of code.

Question 5: Which are the types of variables you might encounter in a PHP code?

PHP has eight variables that are employed in the construction of variables when coding. They include:

  • Integers. These are whole numbers that lack decimals.
  • Doubles. They are numbers with decimals.
  • Booleans. These are logical variables that have only two possible values either true or false.
  • NULL. Contains a single value which is always: NULL.
  • Strings. These are a sequence of characters in a row.
  • Arrays. These are collections of values that have names and indexes.
  • Objects. They are programmer-defined classes that are a combination of other values and functions that are particular to the class itself.
  • Resources. These are unique variables holding references to resources outside PHP.

It’s imperative to go over these basic PHP concepts before an interview as many PHP interview questions will relate to these.

Question 6: What’s the difference between the include () and require () functions?

When using require () function to add a particular file with no success, it results in a fatal error. In the case of include, when the element isn’t found, it will move to the next subsequent step of execution.

Although it’s one of the easiest PHP interview questions, you’d be surprised by how many get this wrong!

Question 7: How do you check if a PHP string contains another string?

There are several ways to check whether a PHP string contains another string or substring (including a character) inside it. We can use the following string functions:

  • strstr returns the first occurence of a substring in a PHP string.
  • stristr is case sensitive, but other than that identical to the strstr function.
  • strrchr searches for the last occurrence of a character in a string.
  • strpos searches for the position of the first occurrence of a substring in a string.
  • strpbrk returns a string from a character identical to any character specified in a string.

Recommended read: If you want to read more about these functions and see some examples on how to use them, we recommend checking out our article on how to check if a PHP string contains another

Question 8: What are the different error types in PHP?

You are likely to meet three types of errors while dealing with PHP and they include:

  • Notices. These are just common simple errors that usually occur in the process of executing a script. An example is when trying to access a variable that is undefined.
  • Warnings. They are more series than notices but when encountered the script will continue to execute the next functions. An instance is the use of include () function when the file to be added is not available.
  • Fatal errors. These types of errors usually lead to the termination of the whole script operation. For instance, if you use the require () function to call a file that doesn’t exist, there will be a fatal error.

This is one of the most important PHP interview questions since when dealing with PHP as a beginner you may need to solve such problems especially during debugging.

Question 9: What is PHP PEAR?

PEAR is the contracted form of PHP Extension and Application Repository. It adds flesh to PHP to enable higher level programming for the development of more sophisticated web browsers. It may also be defined as framework and repository for PHP components that can be reused, usually is has code snippets and libraries.

If you are looking for a more in-depth answer to this question, visit our article about the PHP PEAR framework.

Question 10: How can a PHP script be executed from the command line?

Such task can be accomplished with the help of the command line interface where the following code is keyed in with the specification of the script name:

PHP script.PHP

Question 11: What is the difference between echo and print statements?

These two functions or language constructs are used to output strings in a PHP code. However, echo () has the capability to accept several expressions as opposed to print () which returns Boolean values.

Question 12: How do you increase the execution time of a PHP script?

Normally, the average execution time of a PHP script is thirty seconds set in the PHP.ini file. When you want to increase this time, then you have to modify the max_execution_time in seconds but while maintaining the server environment. That is done to avoid affecting the sites hosted by the server.

Question 13: What is the role of output buffering in PHP?

By default PHP sends data to the web server immediately it is ready to be output there. The data inform of cookies don’t have to be sent at the start of the page hence the need for buffering. With output buffering, cookies can be sent at any point in time based on the stackable property of output buffers.

It would be great if you would also give practical examples regarding your portfolio and how you used output buffering or other concepts addressed by your PHP interview questions.

Question 14: What does a session in PHP programming?

When clients log in to an application, their details get stored in a session variable; such that they are accessible to all the pages within the application. Each visitor per session in PHP is awarded a unique identification.

Question 15: What is the main difference between a session and a cookie?

One of the clear-cut differences between the two is that cookies are stored on the clients’ computers as text documents while sessions are stored in the main server.

In addition to that cookies aren’t capable of storing several variables whereas sessions can handle and store multiple variables for each application.

Sessions cannot be accessed by the users because it is stored on the server. It is majorly for the logging in and out for the applications supported in the server. Cookies, on the other hand, are accessible by the user and are mainly for the tracking of the use activity within site.


After going through this compilation of 14 most common PHP interview questions and their detailed answers, you should be better placed at facing the interview. After all, most companies today are moving to the use of PHP as a server side scripting language. That is because it quickly creates dynamic pages and offers a faster rate of instruction execution. Hence, through our PHP interview questions we give you an edge to be competitive in the programming market. With the knowledge, you have the confidence to pass your interview. Make sure to give your opinion on the PHP questions and answers reviewed here.