JS to PHP

Hi,
I have an HTML page that has some JS functions. the BODY of the html is empty, and the important data I'm writing with one single "document.write" in JS.
I'm trying to get this document.write value, using PHP. Can't really find a way with file_get_contents. What do you think, how can I do it?

Thanks a lot!

if i am understanding what you mean try

readfile()

Unfortunately, I don't think that's what I'm looking for.

Lets say I have a page called b.php. It has a HTML declaration, and some JS functions. In one of those functions, I use this:
var url = "<?echo $_GET['url'];?>";
Then, at the end of this function, I use document.write() to print something.

My other page called a.php. All I want is to get the value of document.write() from b.php in my a.php. Possible?