$re = '/Message: Help\. Reason: (?<firstpart>.*)\n\n.*?@ 1 @ (?<secondpart>.*).$/m';
$str = '@ Timestamp @ ProcessInformation.Process @ <Null> @ Message: Help. Reason: This is going to be cut out at the 256th c
@ Timestamp @ ProcessInformation.Process @ 1 @ haracter.';
preg_match_all($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