$re = '/(?<first>Transaction ID: (?<transId>\w{1,})\.)(.*)(?<second>Reference code: (?<refCode>\w{1,})\.)/m';
$str = 'Your transaction was successful. Transaction ID: 453712046. Reference code: 1234326. Thank you!';
preg_match_all($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