Top 50 PHP interview questions and answers 

PHP is defined as a recursive acronym for PHP Hypertext Preprocessor. It is vastly used as an open-source programming language meant for creating dynamic websites and mobile APIs as well. There are many candidates who are willing to make their career in PHP. 

Here, we are listing some of the PHP interview questions and answers which are collected by our PHP certification training experts. 

1. What do you mean by PHP?

PHP views as Hypertext Preprocessor and is used as an open-source server-side scripting language. It is widely used for the development of websites. 

2. What are the common uses of PHP?

There are different uses of PHP that are following – 

• It is used for performing system functions for creating, opening, reading, and writing them. 
• It is proficient in handling forms in spite of collecting data from files.
• It provides access for adding, deleting, and modifying the elements within the database with the help of PHP. 
• Offer access to the cookies variables and set cookies. 
• With the use of PHP, it is easy for the developers to restrict the users in order to access pages of websites. 

3. How will you define PEAR in PHP?

PEAR exists as a framework and repository for reusable PHP components. It includes all kinds of PHP code snippets and libraries. 

4. Mention the difference between dynamic and static websites

Dynamic websites – In this, the content of the script can easily be changed during the run time. It is simple to understand that the content can easily be regenerated whenever a user visits or reload the website. 

Static websites – Once the script runs, there is no option to change the content. Nothing can be changed even if developers want to. 

5. How can you execute the PHP script from the command line?

For the execution of the PHP script, one has to use PHP Command Line Interface (CLI) and mention the file name of a script.

6. Is PHP considered to be a case-sensitive language?

Well, PHP is considered to be a case-sensitive language. In this, the variable names are definitely case-sensitive, but function names are not.

7. How will you explain the meaning of ‘escaping to PHP’?

The mechanism of differentiating PHP code from other elements with the help of a PHP parsing engine is defined as ‘escaping of PHP’. 

8. Tell us about the characteristics of PHP variables.

Some of the important characteristics of PHP variables are – 

• The variables in PHP are generally denoted by a dollar sign ($).
• The value of variables is known to be the value of recent assignments. 
• Usually, the variables are allocated with the = operator. The variable is generally presented on the left-hand and expression is evaluated on the right side. 
• Variables that are used before they are assigned comprise default values.

9. What is the difference between PHP4 and PHP5?

PHP4 actually does not support oops concept and makes use of Zend Engine 1. On the other hand, PHP5 supports oops concept and highly uses Zend Engine 2. 

10. How many data types are available in PHP?

PHP data types are used for holding various kinds of values or data. Data types including in PHP are 

• Scalar types
• Special types
• Compound types

11. How you can show the output directly to a browser?

In order to display the output directly, then we have to use some special tags like <?= and ?>.

12. How will you define the rules for naming a PHP variable?

For naming a PHP variable, here are the following rules required. 

• It is important that the variable must start with a letter or underscore character.
• A variable name comprises letters, numbers, and underscores, but cannot make use o characters such as +, -, %, (,), &, etc. 

13. How will you define NULL?

NULL is defined to be a special kind of data type that comprises of only one value. A variable that has been assigned the NULL value generally comprises of following properties.

• Evaluate to FALSE in a Boolean context.
• Returns False when it is tested with IsSet() function. 

14. Define a constant including in PHP.

When it comes to defining a constant and retrieving the values of the constant, the users you have to specify the name. A constant can never be changed or remain undefined. 

15. What is the role of the constant() function?

The role of the constant() function is to return the value of the constant. It is helpful in retrieving the value of a constant, but don’t know the name. 

16. Tell the difference between PHP variable and constant.

Variables – variables are written in a dollar sign ($) and can easily be defined by simple assignment. For each path, variables are redefined. 

Constants – They don’t need any kind of sign and can be defined by using the define() function. The best thing about them is that they can be accessed anywhere without focusing on variable scoping rules. 

17. Do multiple inheritances actively supported in PHP?

PHP ideally supports single inheritance. It indicates that a class can get extended from one single class with the help of the keyword ‘extended’.

18. What is the significance of a final class and a final method?

Final in PHP is defined as a class that cannot be extended. While a final method cannot be overridden. 

19. Name the constants available in PHP and what are their purposes. 

Here is a list of constants in PHP. 

_FILE_ It indicates the complete path and filename of the file. 

_LINE_ It shows the current line number of the file. 

_CLASS_ It depicts the class name as it was stated.

_FUNCTION_ It denotes the function name. 

_Method_ It symbolizes the class method name. 

20. What is the role of the continue and break statement?

Continue statement – It is responsible for the loop to skip the remainder and quickly retest the conditions.

Break statement – It is helpful in terminating loop or switch statements and further transferring execution to statement quickly. 

21. How generally do PHP and HTML interact with each other?

Indeed, it is possible for generating HTML via PHP scripts. Moreover, it is also possible to transfer information from HTML to PHP. 

22. What kind of operation is required while passing the values through a form or URL?

If the users want to pass values through a URL or a form, then they have to encode and decode them with the help of htmlspecialchars() and urlencode().

23. How PHP interacts with Javascript?

Generally, PHP and Javascript don’t interact directly because PHP is available as a server side language while Javascript is a client-side language. However, it is possible to exchange the variables. 

24. What are the popular frameworks present in PHP?

There are some of popular frameworks in PHP.

• Codelgniter
• CakePHP
• Yii 2
• Zend Framework
• Symfony

25. Mention some of the data types in PHP.

There are generally 9 primitive data types. 

• Integer
• Boolean
• Float
• String
• Array
• Object
• Callable
• Resource
• Null

26. How you can export data into an Excel file?

A common and trusted method to bring data into a format is supported by Excel. 

Taking an example, it is quite possible to write a .csv file, and a comma is used as a separator in between the fields. 

27. How can you check the value of an available variable is a number?

To check if the variable is numeric or not, one can use the dedicated function to complete the process. 

28. How you can check if a given variable is not having anything and is empty?

If someone wants to check whether the variable is empty or not, then they can make use of an empty() function. 

29. What do you mean by isset() function?

The isset() function is responsible for checking whether the variable is defined and not null. 

30. How will you define PHP parameterized functions?

PHP parameterized functions are available with some parameters. It allows you to pass any amount of parameters inside a function. 

31. What is the meaning of constructor and destructor in PHP?

PHP constructor and destructor are considered to be special kinds of functions that are automatic. The constructor is useful among both because it allows the users to send parameters whenever a new object is created. 

32. What is meant by include and require functions?

The include function is known for putting data of one PHP file into another PHP file. The execution process doesn’t stop even if this function produces a warning. Require function has the same work as the include function. But, if any error occurs it produces a warning and causes a fatal error. 

33. Is it possible to make use of the COM component in PHP?

Indeed, it is completely possible to incorporate Component Object Model (COM) components in PHP scripts that are available as a framework.

34. Describe different errors that can be found in PHP

Generally, there are several kinds of errors available in PHP mentioned as – 

E_Error: It is a fatal error that results in script termination.

E_Warning: This error doesn’t cause any kind of script termination.

E_Notice: It occurred because of an error in the code. 

E_Parse: Compile time parse error.

E_Code_Error: Fatal errors happen at the time of the PHP initial startup.

E_Compile_Error: It indicates that the problem is associated with the script. 

E_CORE_Warning: It occurs at the time of the PHP initial startup.

E_User_Error: It is associated with a user-generated error message. 

E_User-Warning: It is a user-generated warning message. 

E_RECOVARABLE_ERROR: A catchable fatal error signifies a dangerous error. 

E_ALL: This indicates all warnings and errors. 

35. Define the syntax for the ‘forearch’ loop.

The forearch statement is related to using the loop through arrays. For each pass, the value of the current array element is generally assigned to $value. 

36. Mention different kinds of an array in PHP.

Usually, there are 3 categories of arrays found in PHP. 

Associative array: It is a kind of array having strings as an index. It can easily store the element values in collaboration with key values.

Indexed array: An array is defined as an array with a numeric index. In this, the values are accessed and stored in a linear fashion. 

Multidimensional array: This array comprises one or more arrays, that’s why known as a multidimensional array. The values can easily be accessed with the help of multiple indices. 

37. How will you differentiate between a single quoted string and a double quoted string?

Talking about the singly quoted strings, these are treated literally. On the other hand, doubly quoted strings are usually replaced by variables with their values along with specially interpreting character sequences. 

38. What are famous Content Management Systems (CMS) resent in PHP?

There are some popular CMS available in PHP.

WordPress: It is available as a free and open-source content management system (CMS) that depends on MySQL & PHP. It generally includes a template system and plug-in architecture 

Joomla: Joomla is also available as a free and open-source CMS. It is used for distributing web content. This basically depends on a model-view controller web application framework.

Magento: Magento is available as an open source E-trade program that is beneficial for many online businesses. It offers a flexible measured design having different control alternatives. 

39. Explain the difference between ‘echo’ and ‘print’ in PHP. 

PHP echo output has one or more strings. It is a language construct rather than a function. Whereas, PHP print output a string and is available as a language construct, but not a function. 

40. How PHP is different from asp net?

PHP is present as a programming language while ASP NET is known as a programming framework. The websites which are created using ASP.NET make use of C#, whereas PHP gets interpreted. ASP.NET is basically designed for windows machines and PHP offers a free platform and runs on Linux servers. 

41. How will you define ‘echo’ in PHP?

PHP echo is known for output one or more strings. It is available as a language construct rather than a function.  

42. What is the purpose of cookies and sessions in PHP?

Talking about the session first, it is present as a global variable that is stored on the server. Every session is assigned a unique id meant for retrieving the stored values. Generally, the sessions have the power to store large data as compared to cookies. The session values get deleted automatically whenever the browser gets closed. 

43. What is the meaning of overloading and overriding in PHP?

Overloading is known to be defining functions that comprise similar signatures but have different parameters. On the other hand, overriding is relevant to derived classes and the parent class has been defined as a method. In this, the derived class likes to override that method. 

44. What is the use of the goto statement?

The goto statement is used for enabling jumping inside the PHP program. The target is generally indicated by a label followed by a colon. 

45. Define the scope of variables in PHP.

The scope of variables in PHP is pretty clean. All PHP variables work with a single scope that requires files and includes spans. 

46. How can you create a database with the help of PHP and MySQL?

There are some basic steps by which users can create a MySQL database by using PHP.

• First of all, it is important to establish a connection to the MySQL server from a PHP script. 
• Once the connection is successful, then write a SQL query in order to create a database and further store it in a string variable. 
• Now it’s time to execute the query. 

47. Explain the difference between GET and POST methods.

GET – GET restrict the users to send upto 1024 characters. If someone wants to send binary data such as images or word documents, it can’t be possible with GET. QUERY_STRING environmental variable is used for accessing the data that is sent by the GET method. 

POST – When it comes to data size, the POST method doesn’t have any restrictions. Moreover, it is ideal for sending ASC II along with binary data. Whatever data send through the POST method goes through the HTTP header; this means security is based on HTTP protocol. 

48. Why callbackup is used in PHP?

PHP callbackup is present as functions that are known as dynamically by PHP. They are actively used by native functions like array_map, pref_replace_callback, usort, and others. Once you will get access to the callback function, it becomes easy to call whenever required with receiving function.

49. How will you define lambda function in PHP?

A lambda function is defined as an anonymous PHP function that can easily be stored in a variable. It can be passed like an argument to other functions or methods. A closure is also a kind of lambda function that is basically aware of its surrounding context. 

50. Tell us about PHP magic functions/methods.

In PHP, the functions that start with _ names are defined to be magical functions. These are generally identified with two underscore prefixes (_), which function as interceptors that automatically called on specific conditions. PHP offers a number of ‘magic methods known to allow neat tricks in object-oriented programming. 

With this, we have ended up listing PHP interview questions and answers. We hope that these questions will really help you in cracking your interviews. Enroll at PHP Classes in Pune at PRO IT Academy and make your career bright here.