网上搜集的一段php可逆加密函数

function my_encrypt($data, $key='unun.in')
{
$char = $str =  '';
$key    =   md5($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);
}

function my_decrypt($data, $key = 'huYa')
{
$char = $str =  '';
$key = md5($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;
}