Best way to use PHP to encrypt and decrypt?

I plan to store foreign account information for my users on my website, aka rapidshare username and passwords, etc... I want to keep information secure, but i know that if i md5 their information, i can't retrieve it later to use.

Delphi DEC library (Rijndael) encryption

I am trying to use the DEC 3.0 library ( Delphi Encryption Compedium Part I ) to encrypt data in Delphi 7 and send it to a PHP script through POST, where I am decrypting it with mcrypt (RIJNDAEL_256, ECB mode).