how to redirect to new url without changing the current url?

Any traffic comes to a page through any URL like http://www.abc.com or http://chat.abc.com or http://abc.com orhttp://abc.com/a/b.html etc.. should be redirected to
http://www.qwe.com/?dn=abc.com&pid=7PO87OP8X however the URL in the address bar should not change.It should not show http://www.qwe.com/?dn=abcd.com&pid=7PO87OP8X.
How to acheive this?
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