$re = '/^.*where=([a-zA-Z]*).*cat=([^&]*).*|.*cat=([^&]*).*where=([a-zA-Z]*).*$/';
$str = 'http://www.danceclass.es/?s=&where=Sydney+%28Australia%29&company_category=pole&cat=pole&search_simple=STEP+3+-+Show+details
http://www.danceclass.es/?s=&company_category=pole&cat=pole&search_simple=STEP+3+-+Show+details&where=Sydney+%28Australia%29';
preg_match($re, $str, $matches, PREG_OFFSET_CAPTURE, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php