My client wasn't happy with the length of the auto-generated gift certificate codes (16 characters long). Here's the tweak I made to cause the system to generate shorter codes:
In /admin/giftcerts.php look for
Code:
$gcid = strtoupper(md5(uniqid(rand())));
and change this to
Code:
$gcid = substr(strtoupper(md5(uniqid(rand()))),0,6);
This simply trims the original gcid down to the last 6 characters. It should be noted that this statistically reduces the uniqueness of the the Gift Certificate code.
This was done in x-cart gold 4.0.13