php class error after server moved

php class error after server moved

sorry for language becuase i can not talk english good.



i am tired to try forlogin in my cms designed site after server moved.
when i checked pages and php codes,i see one problem. in index page i used
this code always and added new alert code for see result just like this:
$.post("sample.php?",{ myusername: $("#frmus").val() , mypassword:
$("#frmps").val()},function(data)
{
alert(data);
but alert show empty result after server moved . i checked sample.php and
i found one new problem :
when i open sample.php and goto to class definition and seen function
decrypt i see $key returned empty string
public function decrypt($string, $key)
{
$key = substr(hash_hmac($this->hash_method, $key, $this->site_key.
self::HC_KEY), 19, mcrypt_get_key_size($this->cipher,
$this->mode));
// $key returned empty that is my problem here
[continue code ...]
why $key returned empty in after server moved ?!!!! this code always work
correctly but after server moved this code not worked ?!!!
maybe for change version of php ? and if it is so how can fixed this code
? i need help