$re = '/order.*?(\d+)/m';
$str = 'orderId=669819528
url1\\order679638797
url2\\orders\\result691272565
url2\\blahblah&orderId=685442897
url4\\orderId=671554945
otherone
';
preg_match_all($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