Programming :: Transmitting Data Across Webpages?

For a page I'm making, there'll be a "make a friend" link, upon clicking which, the user will be taken to a login page, so that they can authenticate themselves (i.e. WHO wants to make a friend). I want the link to be processed by a "makefriendlogin.php" script which will have "person" as an argument, ie. makefriendlogin.php?person=26 (the number comes from a database, don't worry about it). My question is, how do I write the makefriendlogin.php script, so that the "author" argument will be available to the "makefriend.php" script that'll actually do the authenticating for the user when they enter their name and password?

I thought of something like this:

makefriendlogin.php:
<form method="post" action="makefriend.php">
<input name="username" type="text">
<input name="password" type="password">
<?php

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