RC4加密解密算法 for php

function Rc4 ($pwd, $data){ $key = array(); $box = array();$cipher = ''; $pwd_length = strlen($pwd); $data_length = strlen($data); for ($i = 0; $i < 256; $i++) { $key[$i] = ord($pwd[$i % $pwd_length]); $box[$i] = $i; } for ($j = $i = 0; $i < 256; $i++) { $j = ($j + $box[$i] + $key[$i]) % 256; $tmp = $box[$i]; $box[$i] = $box[$j]; $box[$j] = $tmp; } for ($a = $j = $i = 0; $i < $data_length; $i++) { $a = ($a + 1) % 256; $j = ($j + $box[$a]) % 256; $tmp = $box[$a]; $box[$a] = $box[$j]; $box[$j] = $tmp; $k = $box[(($box[$a] + $box[$j]) % 256)]; $cipher .= chr(ord($data[$i]) ^ $k); } return $cipher;}