The include_once Function

The include_once function includes the specified file in the current PHP script, but only if it has not been included before. This is especially useful when working with files containing function or class declarations to avoid redeclaration errors. The function's parameter is the path to the file to be included.

Syntax

include_once 'path/to/file.php';

Example

Include the config.php file only once:

<?php
	include_once 'config.php';
	include_once 'config.php'; // This call will be ignored
?>

Example

Attempt to include a non-existent file:

<?php
	include_once 'nonexistent.php'; // Will generate a warning, but will not stop script execution
	echo 'Script continues...';
?>

Code execution result:

Warning: include_once(nonexistent.php): failed to open stream: No such file or directory
Script continues...

Example

Using a variable to specify the path:

<?php
	$filePath = 'lib/functions.php';
	include_once $filePath;
?>

The include_once Function

Syntax

Example

Example

Example

See Also