Are you a fresher PHP developer preparing for an interview? Check out these 25 commonly asked interview questions and expert answers to help you ace your PHP developer interview and land your dream job in web development.

As a fresher PHP developer, facing a job interview can be nerve-wracking. However, with the right preparation, you can confidently tackle any interview and increase your chances of landing your dream job in web development. To help you in your preparation, we've compiled a list of the top 25 interview questions that are commonly asked in PHP developer interviews, along with expert answers to guide you.

1. What is PHP?

PHP stands for Hypertext Preprocessor and is a widely-used server-side scripting language for web development. It is known for its simplicity, flexibility, and ability to integrate seamlessly with HTML and databases.

1. What are the basic data types in PHP?

PHP supports several basic data types, including integers, floats, strings, booleans, arrays, and objects.

1. What is the difference between 'echo' and 'print' in PHP?

'Echo' and 'print' are both PHP functions used to output data to the screen. However, 'echo' is slightly faster and can output multiple values at once, while 'print' returns a value (1) and can only output one value at a time.

1. Explain the difference between 'include' and 'require' in PHP.

Both 'include' and 'require' are used to include external files in PHP. However, 'include' will give a warning and continue execution if the file is not found, while 'require' will give a fatal error and stop execution.

1. What is the purpose of the PHP function 'isset()'?

The 'isset()' function in PHP is used to check if a variable is set and not null. It returns true if the variable is set and has a value, and false if the variable is not set or has a null value.

1. How do you prevent SQL injection in PHP?

SQL injection is a common security vulnerability in web applications. To prevent SQL injection in PHP, you can use prepared statements or parameterized queries, which separate SQL queries from user input and automatically handle escaping of special characters. You can also use filter functions like 'filter_var()' to validate and sanitize user input before using it in SQL queries.

1. What is a session in PHP?

A session in PHP is a way to store data on the server that can be accessed across multiple pages or requests by the same user. It allows you to maintain user-specific data, such as login credentials or shopping cart items, throughout a user's browsing session.

1. How do you declare a constant in PHP?

In PHP, you can declare a constant using the 'define()' function. For example:

define('CONSTANT_NAME', 'constant value');

Once a constant is defined, its value cannot be changed throughout the script's execution.

1. What are the different types of error reporting in PHP?

PHP has several levels of error reporting, including 'E_ERROR', 'E_WARNING', 'E_NOTICE', 'E_PARSE', 'E_DEPRECATED', and more. These levels control the severity of error reporting in PHP and can be set using the 'error_reporting' configuration directive or the 'error_reporting()' function.

1. Explain the difference between 'POST' and 'GET' methods in PHP.

'POST' and 'GET' are two common methods used to transfer data from a client (e.g., a web browser) to a server in PHP applications. The main differences between them are:

• 'POST': Data is sent in the body of the HTTP request and is not visible in the URL. It is more secure for sensitive data like passwords, as it is not easily accessible by third parties.

• 'GET': Data is sent in the URL itself as query parameters and is visible in the address bar. It is less secure for sensitive data, as it can be easily accessed and modified by anyone.

1. What is the purpose of the PHP function 'count()'?

The 'count()' function in PHP is used to count the number of elements in an array or the properties of an object. It returns the number of elements or properties in the given array or object.

1. How do you create a session in PHP?

You can create a session in PHP using the 'session_start()' function. It starts a new or resumes an existing session and makes session variables available for storing and retrieving data across multiple pages or requests by the same user.

1. What is the purpose of the PHP function 'header()'?

The 'header()' function in PHP is used to send HTTP headers to the browser, which can be used to control the behavior of web pages. For example, you can use it to set the content type, redirect to another page, or set cookies.

1. How do you connect to a MySQL database in PHP?

To connect to a MySQL database in PHP, you can use the 'mysqli' or 'PDO' extension. Here's an example using 'mysqli':

$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database_name";

$conn = new mysqli($servername, $username, $password, $dbname);

if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

1. Explain the difference between '==', '===', '!=', and '!==' in PHP.

In PHP, '==' is used for loose comparison and checks if two values are equal, disregarding their data types. '===' is used for strict comparison and checks if two values are equal, including their data types. '!=' and '!==' are the negations of '==' and '===', respectively.

1. What is a PHP namespace?

A PHP namespace is a way to encapsulate PHP code into separate "namespaces" to avoid naming conflicts. It allows you to organize your code into separate groups and use classes, functions, and constants without conflicts.

1. What are cookies in PHP?

Cookies are small pieces of data stored on the client's computer by a web server. They can be used to store information like user preferences, session data, and tracking data. In PHP, you can set, retrieve, and delete cookies using the 'setcookie()' and '$_COOKIE' global variable.

1. Explain the concept of inheritance in PHP.

Inheritance is a key concept in object-oriented programming (OOP) where a class can inherit properties and methods from another class. In PHP, you can create a class that inherits from another class using the 'extends' keyword. The child class can then override or extend the properties and methods of the parent class.

1. What are magic methods in PHP?

Magic methods in PHP are special methods with predefined names that are automatically called by PHP in certain situations. For example, '__construct()' is the magic method called when a new object is created, and '__toString()' is the magic method called when an object is used as a string.

1. How do you handle errors and exceptions in PHP?

In PHP, you can handle errors using error handling functions like 'set_error_handler()' and 'set_exception_handler()', which allow you to define custom error and exception handling functions. You can also use the 'try-catch' block to catch and handle exceptions in PHP. The 'try' block contains the code that may throw an exception, and the 'catch' block catches the exception and handles it gracefully.

1. What is the use of the PHP function 'mysqli_real_escape_string()'?

The 'mysqli_real_escape_string()' function is used to escape special characters in a string before it is used in an SQL query. It helps prevent SQL injection attacks by ensuring that any user-supplied data is properly escaped to avoid being interpreted as SQL code.

1. Explain the concept of PDO in PHP.

PDO (PHP Data Objects) is a PHP extension that provides a consistent interface for accessing databases. It allows you to connect to multiple databases using the same code and provides features like prepared statements, which help prevent SQL injection attacks. PDO is a more secure and flexible option for database connectivity in PHP.

1. What are the different types of error reporting in PHP?

PHP has several error reporting levels that determine what types of errors are displayed or logged. The main error reporting levels in PHP are:

• 'E_ERROR': Fatal errors that halt the script execution.

• 'E_WARNING': Non-fatal errors that do not halt the script execution.

• 'E_NOTICE': Warnings about potential issues in the code.

• 'E_ALL': All error types, including notices, warnings, and fatal errors.

You can set the error reporting level using the 'error_reporting' directive in the PHP configuration or using the 'error_reporting()' function in your PHP code.

1. What is the difference between 'require' and 'include' in PHP?

Both 'require' and 'include' are used to include external PHP files in a script, but they behave differently when the included file is not found. 'require' generates a fatal error and halts the script execution, while 'include' generates a warning and allows the script to continue execution. 'require_once' and 'include_once' are similar but prevent the same file from being included multiple times.

1. What is the use of the PHP function 'session_unset()'?

The 'session_unset()' function in PHP is used to remove all registered session variables. It does not destroy the session data, but only clears the values of the session variables. To destroy a session and remove all session data, you can use the 'session_destroy()' function.

In conclusion, these are some of the most commonly asked interview questions for fresher PHP developers. Preparing for these questions and understanding their answers can help you ace your PHP developer interview. Remember to practice coding exercises, review PHP concepts, and showcase your previous projects during the interview to demonstrate your skills and knowledge. Good luck!