$re = '`^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d{3}Z;\d*(?:,\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d{3}Z;\d*)*`m';
$str = '2020-12-31T23:00:00.000Z;15,2021-12-31T23:00:00.000Z;271,2022-12-31T23:00:00.000Z;12,
2020-12-31T23:00:00.000Z;15,2021-12-31T23:00:00.000Z;271,2022-12-31T23:00:00.000Z;12
';
preg_match_all($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