Top 35+ PHP Interview Questions and Answers [2024]

I have made a list of 35+ PHP interview questions and answers that will guide you through this interview-cracking journey for your dream job role. These interview questions have been precisely chosen by industry experts depending on what you are likely to be asked about in the upcoming interviews.

Going through this blog post can boost your chances of getting the attention of hiring managers & hitting the upcoming interviews. This article will give you a clear & concise understanding of the PHP topic. 

Let’s get started!

Q1. Explain the rules for naming a PHP variable.

The following rules are required to be followed while naming a PHP variable;

• A variable must begin with a $ sign followed by the variable name.
• The variable name should start with an underscore, a letter, or a number. 
• Variable names are case-sensitive for some time, so $myvariable & $myVariable are managed as different variables.
• The names of the variables should be meaningful & very descriptive to boost the readability of the code.
• PHP should be a loosely typed programming language & you should not need to declare the data types of variables. 

Q2. What do you mean by PEAR in PHP?

The PEAR in PHP refers to PHP Extension and Application Repository. This is a vital framework as well as a repository for every reusable component of PHP. 

PHP offers different functions & packages. From networking & databases to file remote process control & file system access. It also provides you with various tools to help you easily & quickly develop web services & applications.

PEAR is developed as a centralized platform to create, handle & share reusable PHP elements. 

Q3. Explain the difference between dynamic & static websites.

A static website refers to a website where you can not change the content even after running the script. You can not even modify anything on the website as a web developer, and it is defined previously. 

A dynamic website refers to a website where you can change the content and scripts at run times. Every time a user visits or reloads it, the content is generated again. Every search engine, such as Google, Bing and Yahoo, represents a fully functioning website.

Dynamic websites provide a highly personalized experience, while static websites are highly recommended for informational pages where no frequent content update is essential.

In static websites, the loading speed is higher as the content is pre-rendered. In a dynamic website, the loading speed varies depending on the processing & database queries.

Some famous examples of static websites are landing pages, brochures & portfolios, social media channels, E-commerce sites, and content management systems. 

Q4. How is PHP 4 different from PHP 5? 

PHP 5 is the improved and modified version of PHP 4. The significant difference is the introduction of object-oriented programming or OOP with more significant support for objects or classes like inheritance & visibility. 

Apart from this, PHP 5 provides better performance than PHP 4 because of an optimized Zend Engine 2, which offers higher memory management & speedy execution.

In PHP 4, the call-by-value method is used, while in PHP 5, the call-by-reference method is used. 

Static methods are not used in PHP 4, whereas PHP 5 supports static methods. In PHP 4, constructors have names of the class, whereas in PHP 5, constructors have different names. 

Q5. Do you think PHP is a case-sensitive language?

Yes, PHP is a partially case-sensitive language. The functions are not case-sensitive, whereas variables are highly case-sensitive. 

Variables like $messege & $Messege are treated differently and are case sensitive, while different function names such as Echo, echo & EcHo are viewed equally and assigned for the same function. 

Once you use uppercase for the call & lowercase for the name of the function, it will still be the same function. The rest of the programming language is case-sensitive; even the user-defined functions are not case-sensitive.

Q6. State the difference between constants and variables in PHP.

The significant difference between constants and variables in PHP is that the value of a constant can be modified or changed at the time of the script execution, while you can change the value of the variables during the time of execution.

Through simple assignments, you can not define a constant, but you can possibly define a variable. Constants & variables differ in scope. In variables, the default scope is the only current access scope, whereas constants are accessed all over without employing any scoping rules. 

Q7. State the difference between ‘print’ and ‘echo’ in PHP.

In PHP, both the ‘echo’ & ‘print’ are used mainly to output the vital data or information to the screen. However, they both have some different features, and they are as follows,

• Print is a function which is required in parentheses, while echo is a language that is not necessary in parentheses. 
• Print can output a single string each time, while echo can output multiple strings each time, which are split up with commas.
• Print is slower than echo due to the return value; echo does not return any value. 

Q8. What do you mean by a session in PHP?

A session is a feature of PHP that stores information and allows it to be accessed easily from any page of the website. A session in PHP can generate a file in a temporary location to store all the session variables along with the associated values. 

A session variable can gather data about a single user, making it easily accessible on all the web pages of that application. To store the specific data of a user, a session in PHP needs a unique ID to identify them & monitor their interactions over different web pages without deleting any information. 

Q9. What do you mean by cookies? Explain the ways to create cookies in PHP.

Cookies in PHP refer to the elements that are widely used to recognize unique users in the web architecture. This small file is planted into the client’s system by the server to get vital data from the client for future server development.

Cookies are used to get different features, which are refined by servers depending on the client’s feedback.

The ways to create cookies in PHP are;

• In PHP, you can create a cookie using the “set-cookie ()” function.
•   You should put the name, expiration time, path, domain & value of the cookie as critical parameters. 
• Here, the name is the essential parameter, while other parameters are optional. 

Q10. What are the different types of variables present in PHP?

PHP has eight different types of variables & they are as follows;

Floats: These variables are numbers with specific decimal points.

Arrays: These variables refer to the collection of values.

NULL: This is referred to the variable with no value.

Booleans: These are the variables that have true or false values.

Integers: This variable represents the whole numbers.

Strings: These are sequences of character. 

Objects: These variables refer to the instances of classes that contain functions & data.

Doubles: These are referred to as floating point numbers.

Resources: These variables refer to the particular references to resources that are external to PHP, like connections to databases.

Q11. State the difference between PHP & ASP.NET.

The major difference between ASP.NET & PHP is that ASP.NET is a programming framework, whereas PHP is a programming language. 

ASP.NET is specially designed for Windows, while PHP does not depend on platforms. 

To use ASP.NET, you have to pay for the license associated with it, while PHP is free to use and is an open-source scripting language. 

Q12. Can you explain the difference between require() & include() functions?

Both the require() and include() are applied to add the external PHP files to the web application, but they both have some significant differences. 

With the use of the ‘include()’ function, a web developer can get an error message when the script is still running. 

But the script will stop running once ‘require()’ introduces a fatal error known as E_COMPILE_ERROR. 

Q13. What are some major disadvantages of PHP?

Apart from various perks, using PHP has some disadvantages also, they are:

• PHP is not recommended for sizeable content-based web applications as it is slower than other programming language. 
• PHP is not secure due to its open-source or easy accessibility feature. It is not coded securely; it is open to malicious attacks. 
• PHP lacks debugging tools, which are essential for warning or error detection.
• The old PHP versions lack support for modern modular programming features or functionalities.
• More extensive use of PHP features can lead to poor performance of other web applications.

Q14. What are PHP Magic Functions/ Methods?

The magic method in PHP refers to the functions that are essential build-in methods that begin with a double underscore “_”. These magic functions enable you to do some effective object-oriented programming.

Some examples of PHP Magic Functions/Methods are;

• _destruct()_
• _get()_
• _set()_
• _construct()_
• _call()_
• _isset()_
• _unset()_
• _clone()_
• _invoke()_

Q15. Does JavaScript interact with PHP?

Due to different programming languages, such as PHP being a server-side language & JavaScript being the client-side language, they failed to interact directly. However, through variable sharing and JavaScript code generation via PHP, this is entirely possible.

So, it is possible to pass JavaScript variables to PHP using a simple and clean URL.

Q16. What is the key purpose of @ in PHP?

The ‘@’ in PHP refers to the feature that suppresses error messages that a specific expression can arise. It can also suppress warnings or web errors that you do not want potential users to view. 

If any runtime errors happen in the line that contains the @ symbol at the start, then errors are managed by PHP.

Q17. What are traits?

Traits refer to the specific mechanism that offers some of the applied advantages of various inheritance in programming languages such as PHP, where this inheritance is not supported. Theta allows web developers to apply these combinations of methods again from multiple class hierarchies.

Programmers can reuse a wide range of codes by mixing methods from different classes with the trait.

Q18. What are some different types of Arrays in PHP?

There are three different types of Arrays in PHP, and these include Associative Array, Indexed Array, & Multidimensional Array. 

Associative Array: An associative array refers to the variety with a specific string as an index & helps in storing element values in association with the fundamental values other than strict linear index order.

Indexed Array: An Index array refers to a variety with a specific numeric index. Here, the values are accessed & stored through a linear method. 

Multidimensional Array: A multidimensional array refers to an array that includes one or more arrays. A developer can access values with the help of multiple indices. 

Q19. What are the main types of Errors? Explain. 

Some popular types of errors are;

• E_Error: A script will stop suddenly on an E_Error.
• E_User_Error: It spots an error that was happened by the user.
• E-All: These can capture all errors & warnings.
• E_User_Warning: It offers user-generated warning messages.
• E_Warning: It is used for non-fatal run-time eros or warnings.
• E_Notice: These are non-critical errors that involve identifying undefined variables. 
• E_Parse: These are referred to as syntax errors in code.
• E_Core-Error: These refer to fatal errors in PHP’s core.
• E_Compile_Error: These refer to the errors that occur during script compilation.
• E_User_Notice: These refer to errors that occur along with user-generated notices.
• E_Recoverable_Error: These refer to catchable user errors. 
• E_Strict: These errors recommend code refinements for user compatibility.

Q20. How do you differentiate $$message from $message in PHP?

The major difference between the $message and $$message is that the previous one is a variable and has a fixed value, whereas the last one is a variable saved in another variable. 

Q21. What are some popular & common frameworks in PHP?

Some common & popular frameworks in PHP are;

• Codelgniter.
• Laravel.
• CakePHP.
• Symfony.
• Yii2
• Zend
• PHPixie
• Phalcon
• Slim

Q22. What are some key applications of PHP?

PHP is used to conduct & perform some major functionalities like

• Form handling: PHP helps in collecting valuable data from files, saving them to a file, retrieving them, forwarding data through email & returning the data back to the user. 
• Easy access to cookies & set the variables.
• Entire system performance: PHP helps a developer to open, close, read, write & create files on the system. 
• Data encryption.
• Restriction over users to get easy accessibility over some specific pages of your website. 

Q23. What are the major purposes of continue statement & break in PHP?

The purpose of a break in PHP is to terminate the switch or for loop statement and carry execution to the statement instantly following the switch or for loop.

On the other hand, the primary purpose of a break in PHP is to help the loop skip the remainder of its body & instantly assess its situation before reiterating again. 

Q24. How are Constructors different from Destructors in PHP?

Constructors refer to the process of object creation. These help in initializing the properties of objects. Constructors are used to configure objects accurately and use them immediately.

On the other hand, destructors refer to the process of object destruction and help to clean up resources, such as closing the connection of the database. Destructors help to release resources by closing database connections and managing cleanup tasks.

Q25. Can you name some of the most popular Content Management Systems (CMS) in PHP?

Some popular content management systems (CMS) in PHP are;

• WordPress
• Joomla
• Magento
• Drupal
• October
• Kirby
• Conto
• Frog CMS
• ProcessWire
• News

Q26. State the three different scope levels available in PHP.

The three major scope levels available in PHP are,

• Global Scope
• Local Scope
• Static Scope

Q27. How do you execute a PHP script from the command line?

To execute a PHP script from the command line, you have to follow the below syntax,

Php filename.php.

Q28. What do you mean by overriding & overloading in PHP?

Overriding refers to the process of redefining an inherited way, whereas overloading refers to the process of defining various methods of similar names but with different parameters. 

Overloading has similar signatures and different parameters. 

Q29. Explain the difference between POST & GET methods in PHP.

GET and POST are the two major processes that are widely used for web communication between a client and a server. Post refers to the method of submitting data as a mode of information, while the Get method refers to the method of requesting data.

The Post method is used to send binary data as well as ASCII, while the Get method is not recommended for sending binary data such as Word documents or images to the web server.

Q30. How to connect with MySQL databases in PHP?

As a web developer, you have to use the ‘mysqli_connect()’ command to connect with MySQL databases in PHP. These offer username, database name, password & database host as arguments. To run queries, you can use ‘mysqli_query’. 

Q31. What do you mean by Type hinting in PHP?

Type hinting refers to the PHP function that enables you to highlight the expected data type, identify the quality of the code, and remove bugs.

PHP supports the type hinting feature for callable, scaler types, classes & arrays such as float, bool, int, and string. Arguments are passed to a web function. It also allows you to use the correct data type, mod.

Q32. How to create API in PHP?

If you want to create an API in PHP, you have to follow the below steps:

• Setting up the PHP server.
• Designing your API endpoints highlighting request methods & routes.
• Apply the logic for each endpoint, managing server responses & requests.
• Use appropriate status codes & headers to interact with response states.

Q33. How do you differentiate compile time execution with runtime exception?

Runtime execution refers to the process of execution of a program, such as trying to break down zero or easily access a non-existent file. On the other hand, Compilation time execution refers to the process where a code is translated into a machine language, such as syntax errors.

An excellent example of compile time execution is FileNotFoundException, whereas a good example of a runtime exception is ArrayIndexOutOfBoundException. 

Q34. Explain PDO is PHP. 

PDO refers to the PHP data objectives, which is a database access layer. It offers an effective way to access various databases. PDO offers support to readymade statements that help in limiting SQL injection attacks & make programming code secure.

PDO drivers are easily available for databases like Microsoft SQL Server, Sybase, IBM DB2, FreeTDS and PostgreSQL.

Q35. What is the purpose of namespaces in PHP?

The major purpose of namespaces in PHP is to highlight group-related interfaces, constants, classes and functions combined. These are also used to increase the organization of codes & avoid name arguments. 

These also enable developers to code better and help in handling large projects by developing a hierarchical structure for coding elements.

Q36. What are the major features of PHP variables?

Some significant features of PHP variables are:

• PHP is a complete open-source programming language.
• It offers cross-platform features.
• It is secure & fast.
• It provides active community support.
• Object-oriented programming features such as polymorphism, inheritance, data encapsulation & abstraction are supported by PHP.
• It is easily compatible with different databases such as SQLite & MySQL.
• This independent platform can be run by any operating system, such as Windows, Linux & Unix.

Q37. Can you name some of the Constants in PHP and their purpose?

Some of the popular Constants in PHP are as follows;

• _METHOD_: This constant is used to showcase the entire class method name.
• _LINE_: This specific PHP constant highlights the latest line number of a file.
• _FUNCTION_: This specific constant in PHP is used to highlight the name of the function.
• _FILE_: This displays the full filename & full path of the file. 
• _CLASS_: It is used to return the class name after declaration. 

Q38. What are some major data types in PHP?

There are nine specific types of data types in PHP that come under the three categories of Scaler types, Special Types, & Compound Types. 

Scaler data types are Integer, String, Boolean & Float. Compound data styles include Callable, Array, & Object. And lastly, particular data types are Null & resource. 

Q39. Can you explain some of the major functions of PHP?

Some major functions of PHP are;

• Greg()
• Split()
• Preg_match()
• Preg_split()

Q40. What is the purpose of callback in PHP?

The major purpose of callback in PHP is to execute other parts & it is frequently applied to include customized functionality to the programming code or to offer other ways to execute the code. 

PHP callbacks are used by dynamic functions like preg_replace_callback, array_map & sort. 

Q41. What are the various types of loops in PHP?

The different kinds of loops in PHP are as follows:

• while loop
• do-while loop
• for each loop
• for loop

Q42. Explain some common features of the PHP7

Some major features of PHP7 are as follows:

• Constant arrays using define()
• Spaceship operator
• Generator delegation
• Scalar type declarations 
• Closure::call method
• Anonymous classes
• Generator return expressions
• Group use declaration
• Null coalescing operator (??)
• Return type declarations

Q43. What is meant by PHP acceleration? Mention some of the best PHP accelerators. 

PHP accelerators refer to the elements that are specially designed to boost the overall functionality of PHP-based web applications. It is a vital PHP extension that caches the compiled bytecode, known as Opcode caching.

Some of the best PHP accelerators are:

• Alternative PHP cache
• PHP OPcache
• Windows cache extension for PHP