Way to get and edit GET variables in order to make hyperlinks

Use http_build_query:

<?php
unset($_GET['buyer']);
$_GET['action'] = 'edit';

print '<a href="somefile.php?' . http_build_query($_GET) . '">!!</a>';
?>

I believe you can split up the URI with $parts = parse_url($my_uri), manipulate the resulting array and stick it back together with the http_build_query function.