PHP - Help With Php's Pcre Patterns

Hey everyone!
New member here still getting the hang of PHP. Any help is much appreciated.

Suppose the array contains:
array ('http://www.php.net/styles/site.css', 'http://www.example.com/styles/some.js', 'http://www.domain.net/styles/hey.php');

How do I get php to find the array item that contains let's say "css" and instead of returning just "css" it returns the entire string that has the "css" in it, instance "http://www.php.net/styles/site.css".

I was thinking of using the following:
preg_match('/[SOME_PCRE_PATTERN].css/', 'http://static.php.net/www.php.net/styles/site.css', $matches);

Problem is since the links could be different and have all sorts of different characters in it, I have no idea what to put for the PCRE_PATTERN.

In other words, this:

$links = array ('http://www.php.net/styles/site.css', 'http://www.example.com/styles/some.js', 'http://www.domain.net/styles/hey.php');

foreach ($links as $key) {
 preg_match('/css/', $key, $matches);
 $results[] = $matches;
}
print_r ($results);


Returns this: Array ( [0] => Array ( [0] => css ) [1] => Array ( ) [2] => Array ( ) )

I would like it to return: Array ( [0] => Array ( [0] => http://www.php.net/styles/site.css ) [1] => Array ( ) [2] => Array ( ) )


I hope that makes sense to you guys. Once again, any help is appreciated and thank you!