Hey EyeHawk, I need to use RC4 as well for a project, because it's reversible encryption and there are versions for PHP and ActionScript which makes it very handy for cross platform games.
It would be great if you could add RC4 functionality to your plugin. I could send you the JS RC4 encrypt/decrypt functions.
The output is binary, which is a hassle if you need to use it in a URL for example, so what I normally do in PHP is use PHP's pack() and unpack() functions to convert it to hex
unpack("H*0", rc4crypt::encrypt($password, $string));
returns something like
Which is a lot easier to use.
Then at the other end you'd use PHP's pack() function to return it to it's original form: