$re = '/(?ms)^(?<date>\w+\s\d+)\s+(?<Time>\d+:\d+:\d+).*defaultMsg\":\"(?<defaultMsg>[^\"]+).*userName\":\"(?<userName>[^\"]+)/m';
$str = 'Aug 25 17:41:951 IP_ADDR consolidated_audit: {"affectedEntityList": [{"entityType":"vm","name":"hostname | serverpurpose","uuid":"Ilaef477-6f03-4a22-baa7-23736c8e741c"}],"alertUid":"VmUpdateAudit","classificationList":["UserAction"],"creationTimestampUsecs": "1629874233889978",["defaultMsg":"Updated VM hostname serverpurpose","opEndTimestampUsecs","1629874233884373","opStartTimestampUsecs","1629874233779524","operationType";"Update","originatingClusterUuid":"0005ad50-f430-a46c-001e-e4434bb76b0e","params":{"is_secure_boot":"false","is_uefi_boot":"true","vm_name":"hostname | serverpurpose"}, "recordType": "Audit","severity":"Audit","userName":"abc@abc.com","userUuid":"3f73d040-7516-5caa-a956-91179b2cblf5","uuid":"254f3952-bf9b-4205-8al4-ad2074ed70ab"}';
preg_match_all($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