$re = '/(?:id=(?<ID_Firewall>\w+) )(?:.*time="(?<timestamp>(?:[0-9]{4})-(?:[0-9]{2})-(?:[0-9]{2}) (?:[0-9]{2}):(?:[0-9]{2}):(?:[0-9]{2}))")(?: fw=(?<IP_Firewall>[[:graph:]]+))(?: pri=(?<Niveau>(?:[0-9]{1,2})))(?:.*m=(?<ID_Event>[[:graph:]]+))(?:.*?msg="(?<Description>[^"]+))(?:.*srcMac=(?<MAC_Source>[[:graph:]]+))?(?:.*src=(?<IP_Source>(?:[[:digit:]]+\.){3}(?:[[:digit:]]+))?)(?::(?<Port_Source>[[:digit:]]+)?)(?::(?<INT_Source>[[:graph:]]+))(?:.*srcZone=(?<Zone_Source>[[:graph:]]+))?(?:.*natSrc=(?<NAT_Source>(?:[[:digit:]]+\.){3}(?:[[:digit:]]+))?)?(?::(?<NAT_Port_Source>[[:digit:]]+)?)?(?:.*dstMac=(?<MAC_Destination>[[:graph:]]+))?(?:.*dst=(?<IP_Destination>(?:[[:digit:]]+\.){3}(?:[[:digit:]]+))?)(?::(?<Port_Destination>[[:digit:]]+)?)(?::(?<INT_Destination>[[:graph:]]+))(?:.*dstZone=(?<Zone_Destination>[[:graph:]]+))?(?:.*natDst=(?<NAT_Destination>(?:[[:digit:]]+\.){3}(?:[[:digit:]]+))?)?(?::(?<NAT_Port_Destination>[[:digit:]]+)?)?(?:.*usr="(?<Utilisateur>[^"]+))?(?:.*proto=(?<Protocole>[[:graph:]]+))?(?:.*rule="(?<Regle>[^"]+))?(?:.*appName="(?<Nom_Application>[^"]+))?(?:.*dstname=(?<Nom_Destination>[[:graph:]]+))?(?:.*arg=(?<Argument_DST>[[:graph:]]+))?(?:.*Category="(?<Categorie>[^"]+))?(?:.*note="(?<Note>[^"]+))?/m';
$str = '<134> id=FIREWALL_SYSLOG time="2019-03-21 12:30:24" fw=1.1.1.1 pri=6 c=1024 gcat=6 m=537 msg="Connection Closed" srcMac=aa:bb:cc:dd:ee:ff src=2.2.2.2:12345:X1 srcZone=LAN natSrc=3.3.3.3:54321 dstMac=gg:hh:ii:jj:kk:ll dst=4.4.4.4:443:X2 dstZone=WAN natDst=5.5.5.5:443 usr="Unknown" proto=tcp/https sent=1348 rcvd=8230 spkt=10 rpkt=9 cdur=2266 rule="(WAN->WAN)" app=49177 appName="HTTPS" n=55917537';
preg_match_all($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