$re = '/^\[(?<timestamp>\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z)\s+(?<level>\w+)\s+(?<module>\w+)\]\s+(?<body>.*)$/m';
$str = '[2017-11-09T02:12:24Z DEBUG my_app] this is a debug message
[2017-11-09T02:12:24Z ERROR my_app] this is printed by default
[2017-11-09T02:12:24Z INFO my_app] the answer was: 12';
preg_match_all($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