What your saying makes sense, but just to be completely clear, there is no possibility for collision when encrypting?
Also, any opinions on doing something like...
and then on the flip side
$data = base64_encode('||1221-15252||');
$translated = str_replace('=', '', strtr(base64_encode($data), '+/', '-_')) . 'aAn';
It seems like its still "never gone" similar to encryption, but it doesnt require mcrypt and it just tacks on something extra to the end to confuse anyone that would attempt a base64_decode()
$decoded = base64_decode(strtr(substr($translated, 0, -3), '-_', '+/'));