Resaltando busquedas de Google con PHP

	function filtro($val) {
		return strpos($val, 'q=') === 0;
	}
	$url = $_SERVER['HTTP_REFERER']; 
	$url = parse_url($url);
	$url = $url['query'];
	$parametros = split("&", $url);
	$cadena = array_filter($parametros, "filtro");
	$cadena = urldecode(substr(array_shift($cadena), 2));
	ob_start();

	$html = ob_get_clean();
	$palabras = split(" ",$cadena);
	foreach ($palabras as $palabra) {
		$html = preg_replace('/('.$palabra.')/i', '<b>$1</b>', $html);
	}
	echo $html;