PHP Basic Auth Gateway. Requests basic auth (password is reversed username) and redirects to URL passed as query string

login.php

<?php
$username = 1;
$revpwd = 0;
if (isset($_SERVER['PHP_AUTH_USER']) and isset($_SERVER['PHP_AUTH_PW'])) {
	$username = $_SERVER['PHP_AUTH_USER'];
	$password = $_SERVER['PHP_AUTH_PW'];
	$revpwd = strrev($password);
}
if ($username == $revpwd) {
	if (isset($_SERVER['QUERY_STRING'])) {
		header("Location: " . $_SERVER['QUERY_STRING']);
			
	}
	else {
		echo "<p>Hallo {$_SERVER['PHP_AUTH_USER']}.</p>";
		echo "<p>Set redirect target in query string, e.g. append <code>?http://schapiro.org</code> to the URL.</p>";
			
	}
}
else {
	header('WWW-Authenticate: Basic realm="Login Test"');
	header('HTTP/1.0 401 Unauthorized');
	echo '<p>Password is reversed Username</p>';
}
?>