I couldn't easily find an example of how to verify if someone added my link to their site while they added their link to a directory of mine. After some research, I found out how to search for a string remotely. I have simplified the steps so that you get the gist of it and can modify the code as necessary.

//// (PHP 4 >= 4.3.0, PHP 5) 
 
$haystack = file_get_contents('http://lvgloves.com/testing/'); 
$needle = '<a target="_blank" title="PHP and Flash Development" href="http://www.vectorflash.net">Vectorflash.net</a>';
 
if( stristr($haystack,$needle) != FALSE )
{
	echo 'There is a match.';
}