$url = (isset ($_GET['url']) && file_exists($_GET['url'])) ? "files/" . strtolower($_GET['track']) : "http://example.com/404.html";
$url = (isset ($_GET['track']) && file_exists("files/" . $_GET['track'])) ? "files/" . strtolower($_GET['track']) : "http://example.com/404.html";
$url = (isset ($_GET['track']) && file_exists("files/".strtolower($_GET['track']).".html")) ? "files/".strtolower($_GET['track']).".html" : "http://example.com/404.html";
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