Autoloader functions
Yes, you could put that into a separate file and include_once('header_file.php');.

You try something such as:

function loadFile($name, $isInterface = false) {
    $type = ($isInterface == true) ? 'interface' : 'class'
    $path = sprintf('./classes/%s.%s.php',$name,$type);
    if (file_exists($path)) {
        require_once($path);
    }
}