I read elsewhere in StackExchange that it's not possible to decrypt AES strings originating from AMPScript in PHP. Is this true? It seems that it should be possible with mcrypt.
Also, part two for this question... if AES isn't possible, then should we go with DES or TripleDES? We need to be able to decrypt data generated in ExactTarget's EncryptSymmetric() function in a clients's PHP environment.