$re = '/\b(\w[a-zA-Z].*\Dapp=SNMP.+)/m';
$str = 'Oct 3 11:34:03 1.1.1.1 CEF:0|FORCEPOINT|Firewall|6.5.1|70018|Connection_Allowed|0|app=SNMP (UDP) rt=Oct 03 2019 11:28:12 deviceFacility=Packet Filtering act=Allow deviceOutboundInterface=13 deviceInboundInterface=0 proto=17 dpt=161 spt=62032 dst=2.2.2.2 src=3.3.3.3 dvchost=4.4.4.4 dvc=4.4.4.4 deviceExternalId=company-name node 1 cs1Label=RuleID cs1=2097272.10';
preg_match_all($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