What is the difference between require_once and require in PHP?

Answer 1

require()
The require() function is identical to include(), except that it handles errors differently. If an error occurs, the include() function generates a warning, but the script will continue execution. The require() generates a fatal error, and the script will stop.

require_once()
The require_once() statement is identical to require() except PHP will check if the file has already been included, and if so, not include (require) it again.

Answer 2

The require statement has two variations, require and require_once.

The require/require_once statement is used to include file.

Require_once is ignored if the required file has already been added by any of the four include statements.
It has the following syntax:

<?php
require 'file_name';
?>

<?php
require_once 'file_name';
?>