$re = '/^(?<Date>\d+-\d+-\d+\s+\d+:\d+:\d+)\s+\[[^\]]*\]\s*\[(?<Process>[^\]]*)\]\s*\[(?<Step>[^\]]*)\]\s*\[(?<User>[^\]]*)\]\s*[^\[]+\s\[(?<Log_level>[^\]]+)/m';
$str = '2021-09-28 10:20:27 [machine-run-76416-hit-644640-step-12470][Business Process Name][Business Process Step Name][Bot Users] MetadataStorage [ERROR] Boot failed
2022-04-04 23:30:16 [http-nio-127.0.0.1-7080-exec-3] [] [] [] DataBaseChecker [DEBUG] Checking MySQL ...
2022-04-04 23:30:16 [http-nio-127.0.0.1-7080-exec-3] [] [] [] DatabaseVersionChecker [INFO] Database is up to date.
2022-04-04 23:30:16 [http-nio-127.0.0.1-7080-exec-3] [] [] [] DataBaseChecker [DEBUG] Checking PostgreSQL ...
2022-04-04 23:30:16 [http-nio-127.0.0.1-7080-exec-3] [] [] [] OcrHealthChecker [DEBUG] Checking OCR ...';
preg_match_all($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