$re = '/([\w-]+?)=(".*?"|\S+)/';
$str = 'appName=XXX clientIp=X.X.X timestamp="2017-06-05T13:22:12-07:00" request="POST /forward HTTP/1.1" statusCode=204 bytesOut=1167 totalTime=0.062 bytesIn=1289 sourceHost=XXXX connId=49936598 connReqs=9 upInstance=XXX:104:XXX-XXX:8664:17F34 upConnectSec=0.052 upAddr="XX.XX.XX:123" upHost="vcv08it-cvcv2801:8464" upHdrTimeSec=0.058 upRespTimeSec=0.058 pid=32561  upStatusCode=204 message="Access Log" corrKey=GMIFCDIKRZR2T4VZQXJA2IT6 upCached=- length=0 partition=XXX location="= /v1/tXXXX" xff="XX.XX.XX.XX" referer="-" user-agent="Apache-HttpAsyncClient/4.1.1 (Java/1.8.0_131)\\" rateLimitCurrentValues="--" rateLimitTimeMs=\\"-:-"
';
preg_match_all($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