$re = '/(?<field1>[^\:]+)\s+?\:\s+?(?<field2>[^\[]+)\s+?\[(?<date>[^\]]+)\]\s+?\:\s+?(?<field4>[^\:]+)\s+?\:\s+?(?<field5>[^$]+)/';
$str = 'INFO : LM_36488 [Thu Jan 18 17:00:18 2018] : (11616|15356) Session task instance [Big_Data_Job] : [TM_6721 Started [Fetch Session from Repository].]';
preg_match_all($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