$re = '/(?:(?<=\s)\w+(?=\[))|(?:(?<=>)\w+(?=\[|:))/m';
$str = '<103>CP-MGMT xpand[2859]: Configuration changed from localhost by user admin by the service dbset
<31>routed[4006]: rt_instance_monitor_job: scheduled next instance monitor in 5 seconds
<134>CP_FireWall: 2Jul2017 18:52:23 accept ip address message';
preg_match_all($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