PHP加密解密类

<?php
class Mypass {

    static function encrypt($data, $key){
        $key = md5($key);
        $x  = 0;
        $len = strlen($data);
        $l  = strlen($key);
        for ($i = 0; $i < $len; $i++){
            if ($x == $l){
                $x = 0;
            }
            $char .= $key{$x};
            $x++;
        }
        for ($i = 0; $i < $len; $i++){
            $str .= chr(ord($data{$i}) + (ord($char{$i})) % 256);
        }
        return base64_encode($str);
    }

    static function decrypt($data, $key){
     $key = md5($key);
        $x = 0;
        $data = base64_decode($data);
        $len = strlen($data);
        $l = strlen($key);
        for ($i = 0; $i < $len; $i++)
        {
            if ($x == $l)
            {
             $x = 0;
            }
            $char .= substr($key, $x, 1);
            $x++;
        }
        for ($i = 0; $i < $len; $i++)
        {
            if (ord(substr($data, $i, 1)) < ord(substr($char, $i, 1)))
            {
                $str .= chr((ord(substr($data, $i, 1)) + 256) - ord(substr($char, $i, 1)));
            }
            else
            {
                $str .= chr(ord(substr($data, $i, 1)) - ord(substr($char, $i, 1)));
            }
        }
        return $str;
    }

}

/*
$data = ‘PHP加密解密算法‘;  // 被加密信息
$key = ‘123‘;     // 密钥
$encrypt = encrypt($data, $key);
$decrypt = decrypt($encrypt, $key);
echo $encrypt, "n", $decrypt;

*/
?>