$re = '/^([^:]+::\s*){2}(?<short_message>.*)::/m';
$str = 'Alert :: Critical :: NXUSWSDD01 :: DATA-DOMAIN-MIB:spaceOver90Percent : sysUpTime = 33 days 22 hours 7 minutes 10.56 seconds, systemSerialNumber = APM00202524576, fileSystemSpaceUsed.2 = 26637.6, alertInfoDescription.48 = Space usage in Data Collection has exceeded 90% threshold. EVT-OBJ::FilesysType=2 EVT-INFO::SpaceUsage(%)=90 :: Storage Traps
Alert::Serious::Server::Memory Utilization is 92 %, which is above threshold 90% & less than 95%::memory.';
preg_match_all($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