$re = '/\/\/(?:www\.)?(.+?)\//';
$str = '(http://web.archive.org/web/20080620033027/http://www.mrvc.indianrail.gov.in/overview.htm)';
preg_match_all($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