This snippet of PHP code takes any shortened URL, like those from Bitly, Google or Twitter, and expands it into the full and final destination URL.

function expandShortUrl($url)
{
	$headers = get_headers($url, 1);

	$loc = $headers['Location'];
	if(is_array($loc))
	{
		// get the highest numeric index
		$key = max(array_keys( $loc));
		return $loc[$key];
	}
	else
	{
		return $loc;
	}
}

Hat Tip: Deluxe Blog Tips and Karl Groves – Easily Expand Short URL Using PHP