$re = '/([^\s=]+)=(?|"([^"]*)"|(\S+))/i';
$str = 'date=2019-05-10 time=11:50:48 logid="0001000014" type="traffic" subtype="local" level="notice" vd="vdom1" eventtime=1557514248379911176 srcip=172.16.200.254 srcport=62024 srcintf="port11" srcintfrole="undefined" dstip=172.16.200.2 dstport=443 dstintf="vdom1" dstintfrole="undefined" sessionid=107478 proto=6 action="server-rst" policyid=0 policytype="local-in-policy" service="HTTPS" dstcountry="Reserved" srccountry="Reserved" trandisp="noop" app="Web Management(HTTPS)" duration=5 sentbyte=1247 rcvdbyte=1719 sentpkt=5 rcvdpkt=6 appcat="unscanned"
';
preg_match_all($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