Need help with greating custom payment gw module

[johny.d]

Been working on a custom gw module for some time now, I have a problem with the code.

I found the problem but i dont know how to solve it.

 

When i changed following codes, payment gateway works 100%.

$return = "http://domain.com/1";
$cancel = "http://domain.com/2";
$reject = "http://domain.com/3";
$delayed = "http://domain.com/4";

 

but examble if i use other links like following code it wont work, and i get that there is md5 error.

 

$return = "http://domain.com/return";
$cancel = "http://domain.com/whmcs";
$reject = "http://domain.com/reject";
$delayed = "http://domain.com/delayed";

 

That is very strange, do you have any idea about that?

I have done all what they need in API, and there is no any demands how the links must be.

 

Full code here:

http://slexy.org/view/s20xjYc3wo

 

Any idea what could be causing this?