So what you want, based your example is, if I go to:
http://www.MYPAGE.com/page.php?id=35
You want the RSS data to show from:
http://www.test.com/?p=28
If that is true then all you need to do is create a table in your mysql that will hold the rss feed url and any other data about the feed... Each record in that table will have a primary key value that you can reference in your websites url
So for instance
http://www.MYPAGE.com/page.php?id=35
In page.php you can pull the value for $_GET['id'] and use it in your mysql query
$query = "select * from feeds where feedid = '".$_GET['id']."'";
The above assumes your table is called feeds
now you can parse the results of the query and use either DOM or SIMPLEXML to load the external RSS data and display it on your site.
