PHP require_once()

The require_once() function in PHP is used to include a PHP file into another PHP file. It is similar to the include() function, but there is an important difference - if the file being included has already been included once, require_once() will not include it again.

Syntax

require_once 'filename.php';

Example

Let's assume we have a file myfunctions.php that contains some functions that we want to use in our main script.

// myfunctions.php
function greeting($name) {
   echo "Hello, $name!";
}

In our main script, we can use require_once() to include the myfunctions.php file and then call the greeting() function.

// main.php
require_once 'myfunctions.php';
greeting('John'); // Output: Hello, John!

Output

The output of the example above will be:

Hello, John!

Explanation

require_once() works the same way as require(), but it checks if the file has already been included and will not include it again. This is useful in situations where you need to make sure that a file is included only once in your script.

Use

The require_once() function is mostly used in PHP frameworks and applications where files are included multiple times. It ensures that a required file is only loaded once, which helps to keep your code organized and efficient.

Important Points

• require_once() is similar to require(), but it checks if the file has already been included and will not include it again.
• If the file specified in require_once() is not found, the script will terminate with a fatal error.
• require_once() can also be used with absolute paths. For example, require_once '/usr/local/include/myfile.php';.

Summary

The require_once() function in PHP is a useful tool for including files in your scripts. It ensures that each file is only included once, which helps to keep your code organized and efficient. However, if the file specified in require_once() is not found, the script will terminate with a fatal error.