I\'m making now things with php + Symfony2 framework, and I have the following code:
require_once(\"one_file.php\"); require_once(\"another_file.php\");
You want to follow these other answers, especially the approved one, but if you are using a third party library with tons of PHP files, you can do require_once(__DIR__.'/path/to/file.php') as a quick fix.
require_once(__DIR__.'/path/to/file.php')