$re = '/^\/t(?:\/(\d+)\/[a-z_-]+\/?|op(\d+)\.html)$/im';
$str = 'good examples:
/t/2/title/
/t/98127/welcome_world-here/
/top1.html
/top2126.html
/top102542/120939.html
bad examples: #should not match
/top2120/welcome/
/t/2121.html
/t/2124/bla.html
/blabla21051.html
';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($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