$re = '/(\x23[^\x2c]+)\x2c[[:space:]]start[[:space:]][[:digit:]]{4}\x2d[[:digit:]]{2}\x2d[[:digit:]]{2}[[:space:]]([^[:space:]]+)[[:space:]][^\x2c]+\x2c[^\x2c]+\x2c[[:space:]](captureme)/m';
$str = 'Message #1243669, start 2018-12-17 16:32:50 CET, duration 20, captureme';
preg_match_all($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