<?php
$line = "07-28-14 21:59:58_gateway:Sybase, gatewayID:1048, mobile:447973223963, referenceID:1912081231, status:Message 1 of the order 1912081231 at destination of 447973223963 has been received at 22:59:55 (CET) on the 28-07-2014., statusParsed:delivered, statusCode:, sendDate:28-07-2014, sendTime:22:59:55";
preg_match("/_gateway:(.[^,]*)/", $line, $matches);
echo $matches[1];