Call a PHP file from the main file

I want to arrange my codes properly by starting to separate the codes like uploading files, from the index.php, How can i call th开发者_如何学Pythone upload.php in the index.php? The upload.php is not a function. Is it possible?

<?php include('upload.php');?> at the top of index.php

<?php 

require_once 'upload.php';

//no close tag if you have no html code