RC4/ARCFOUR Implementation in PHP

I wrote this RC4/ARCFOUR implementation in PHP – based on the original C source code posted on usenet in 1994. The rc4() call itself is completely self-contained, two other methods rc4_test() and rc4_benchmark() have been provided for testing and are optional.
My motivation for writing it was to replace the dependency on MCrypt in my SpamKit plugin for WordPress – see Gerry‘s site for the updated TBT code I will wrap in the next SpamKit Plugin release.
This is software is completely public domain, all I ask for is a simple credit for my work if you find it useful.
View Source: rc4.php
View Source: rc4tests.php
Examples:
1. Simple encryption & decryption
[php]< ?php require_once( "rc4.php" ); $key = "0123456789abcdef"; $plaintext = "Hello World!"; $ciphertext = rc4( $key, $plaintext ); $decrypted = rc4( $key, $ciphertext ); echo $decrypted . " - " . $plaintext . "\n"; ?>[/php]
2. Execute the tests and display the results
[php]< ?php require_once( "rc4tests.php" ); // Auto includes rc4.php echo rc4_tests(); ?>[/php]
3. Execute the tests as benchmarks and display the results
[php]< ?php require_once( "rc4tests.php" ); // Auto includes rc4.php echo rc4_benchmark(); ?>[/php]