i need something to get (youtube & metacafe &..)videos thumbnail

i trying use this ..but didn’t work well ..
<?

// we make a function, so it will easy to applicate

function getinput($url)

{

$regexp= "http:\/\/www\.youtube\.com\/watch\?v=(.*)(.*)";
if(preg_match_all("/$regexp/siu", $url, $matches))

return $matches[1][0];

}

// Catch Youtube Thumbnail Image from IRON MAN 2 UPDATE MOVIE

$youtube_url = “http://www.youtube.com/watch?v=1TiYlG21VAQ”;
$thumbnail_of_youtube = getinput($youtube_url);

// The thumbnail image of Youtube always has a pattern like this : http://i1.ytimg.com/vi/[videoid]/default.jpg

echo ‘‘;

?>

so can any one help me please ..