Script verursacht "Internal Server Error"

$Input  = preg_replace("/[^0-9a-zA-Z]/" , '' , $Input); 
	preg_match('/\A([7]{1}[8]{1}[0-9]{2}[.]?[0-9]{3}[.]?[0-9]{3})[a-zA-Z0-9_]*?([0-9]{8})\z/', $Input, $h);
	$Ident = preg_replace_callback(
    '/\A([7]{1}[8]{1}[0-9]{2}[.]?[0-9]{3}[.]?[0-9]{3})[a-zA-Z0-9_]*?([0-9]{8})\z/',
    function ($h) {
        return preg_replace('/(?<=...)(?=(...)+\z)/', '.', $h[1])
            . '_'
            . $h[2];
    },
    $Input
	);