Encoding & Decoding

[Fwks08]

Is there an easy way to encode and then decode a string in PHP? It's probably base64, but I'd like to add a custom string to make it un-decodable without the string. I hope I haven't lost anyone.

eg,

$code = 'encode me';

$str = base64_encode("blah".$code);

How would I decode that?