Karlosp.net

function unicode_urldecode($url) {
	preg_match_all('/%u([[:alnum:]]{4})/', $url, $a);

	foreach ($a[1] as $uniord) {
	   $utf = '&#x' . $uniord . ';';
	   $url = str_replace('%u'.$uniord, $utf, $url);
	}
	return urldecode($url);
}

Usage:

$content = unicode_urldecode($_GET['content']);