How to use the include_once statement in PHP?

@denis 

The include_once statement in PHP is used to include a file in a PHP script. It is similar to the include statement, but with one important difference: if the file has already been included, it will not be included again.

Here's the basic syntax of include_once statement in PHP:

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include_once 'filename.php';

In this syntax, filename.php is the name of the file you want to include. The include_once statement will look for the file in the same directory as the PHP script that is calling it.

If the file is found, it will be included in the script. If the file has already been included, the include_once statement will not include it again.

Here's an example that demonstrates how to use include_once statement in PHP:

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<?php
include_once 'header.php';

// Your PHP code here

include_once 'footer.php';
?>

In this example, the header.php file is included at the beginning of the script, and the footer.php file is included at the end of the script. If either of these files has already been included, the include_once statement will not include them again.