$re = '/(?:\d{2}:\d{2}:\d{2} - (?:\[[^\]]*\] )?)([\w: -]+)/';
$str = 'INFO: Device 6: Time 20.11.2015 06:28:00 - [Script] FunFehlerButton: Execute [0031 text]
and
INFO: Device 0: Time 09.12.2015 03:51:44 - [Replication] FunFehlerButton: Execute
and
INFO: Device 6: Time 20.11.2015 06:28:00 - FunFehlerButton: Execute';
preg_match_all($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