Top 10 PHP Programming Interview Questions and Answers for Web Developers

PHP is a popular programming language used for web development. Here are some common interview questions and answers for PHP developers:

1) What is the difference between single-quoted and double-quoted strings in PHP?

Single-quoted strings are slightly faster and don’t support escape sequences. Double-quoted strings support escape sequences and variable interpolation.

2) What is the difference between include and require in PHP?

Both include and require are used to include a file into another, but when a file is included with the require statement and the file is not found, it will cause a fatal error and stop the script. On the other hand, if a file is included with the include statement and the file is not found, a warning will be issued, but the script will continue to execute.

3) How can you pass data from one PHP script to another?

There are several ways to pass data from one PHP script to another: through query strings, through sessions, and cookies.

4) What is the difference between GET and POST methods in PHP?

The GET method is used to retrieve data from the server, while the POST method is used to send data to the server. GET requests are visible in the URL, while POST requests are not. GET requests have a limit on the amount of data that can be sent, while POST requests do not.

5) How can you connect to a database in PHP?

To connect to a database in PHP, you can use the MySQLi or PDO extension. You will need to provide the hostname, username, password, and database name to connect to the database. Once connected, you can use SQL statements to query and manipulate the data in the database.

6) How can you prevent SQL injection in PHP?

SQL injection can be prevented by using prepared statements with bound parameters, or by using parameterized queries. These techniques ensure that user input is properly sanitized and does not modify the intended SQL query. It’s also important to always validate and sanitize any user input before using it in a query.

7) What is the difference between == and === in PHP?

The == operator compares the values of two variables, while the === operator compares both the values and the data types of two variables. The === operator will only return true if the variables being compared have the same value and are of the same data type.

8) How can you create a session in PHP?

To create a session in PHP, you need to call the session_start() function at the beginning of the script. Once a session is started, you can store and retrieve data in the $_SESSION array.

9) How can you create a cookie in PHP?

To create a cookie in PHP, you can use the setcookie() function. This function takes the name of the cookie, the value, and the expiration time as parameters. Once a cookie is set, you can retrieve its value using the $_COOKIE array.

10) What is the difference between a session and a cookie in PHP?

Sessions are stored on the server and are used to store data that is specific to a particular user. Cookies are stored on the client’s computer and are used to store data that can be accessed across multiple pages or visits to a website. Sessions are more secure than cookies as they are stored on the server and are not accessible to the client.

It’s also important to mention that, as a best practice, always validate and sanitize any user input before using it.