function compresscss ( $data, $url ) {
global $current_css_url;
$current_css_url = $url;
/* remove comments */
$data = preg_replace('!/\*[^*]*\*+([^/][^*]*\*+)*/!', '', $data);
/* remove tabs, spaces, new lines, etc. */
$data = str_replace(array("\r\n", "\r", "\n", "\t", ' ', ' ', ' '), ' ', $data);
/* remove unnecessary spaces */
$data = preg_replace('/[ ]+([{};,:])/', '\1', $data);
$data = preg_replace('/([{};,:])[ ]+/', '\1', $data);
/* remove empty class */
$data = preg_replace('/(\}([^\}]*\{\})+)/', '}', $data);
/* remove PHP code */
$data = preg_replace('/<\?(.*?)\?>/mix', '', $data);
/* replace url*/
$data = preg_replace_callback('/url\(([^\)]*)\)/', 'replaceurl', $data);
return $data;
}