a simple javascript development (just a few lines)

There are 2 different sites, let's call them: 1- [login to view URL] 2- [login to view URL] In [login to view URL], I will have a HTML code like this: <script type="application/javascript" src="[login to view URL]"></script> In [login to view URL], we will have "[login to view URL]". Its task is: 1- read variable "getid" and make sure its an integer between A and B (output an error message if not) 2- make sure HTTP_REFERRER that is calling it fits to a alloweddomain list ([login to view URL] etc.) (output an error message if not) 3- If both conditions are met, call this url via ajax [login to view URL] and output anything that php file returns in [login to view URL] page. So basically what I need is a simple javascript which gets a GET variable from a html page from a different domain, parse this variable and pass it to a PHP file and then return the result of the PHP file to the calling page. I need you to code ONLY "[login to view URL]" javascript file which I expect to be a just a few lines of a script. You are free to use jquery or standalone javascript. You are NOT expected to code "[login to view URL]" file, I will code it. I will NOT give you access to either site, you will just send me .js file and I will upload it to the server myself. I also need something who can do it fast. It will be probably a few lines so I don't expect a performance issue but still I need to say it needs to be running fast because it will be called very frequently from the remote server with a lot of calls (eg. 1000 calls in single page load). I'm aware you can't control php part, nor server speed so I just need its algoritm to be fast and clean.