$url_v = "http://example.com";
if  (isset($_GET['url'])){ $url_v = $_GET['url']; }
$url_v = trim($url_v, "'\\");

// remove strings with 5 letters where
// a lowercase letter is followed by an upper case
$n_replacements = 0;
$l='[a-z]'; $u='[A-Z]'; $a='[a-zA-Z]';
$patt = "/\/" . $l . $u . $a . $a . $a . "\//";
$url_v = preg_replace($patt, "/", $url_v, -1, $count);
$n_replacements += $count;
$patt = "/\/" . $a . $l . $u . $a . $a . "\//";
...
...
<script type="text/javascript">location.href = '<? echo $url_v; ?>';</script>