I have php scripts that do nightly backups

each one works fine when executed by itself

I want to reduce the number of cronjobs, so tried to combine them into a single script

require_once "dbBackup.php";
require_once "siteBackup.php";
require_once "ordersBackup.php";
require_once "mediaBackup.php";

only the first 2 get executed

it doesn't matter which order I write them in, it's always just the first two

what is going on?!