$re = '/caller\"\s*:\s*\{\s*\"id\":\s*\"(?<callerid>[^\"]+)?\"\,\s*\"version\"\s*:\s*\"(?<callerversion>[^\"]+)?\"/m';
$str = '{
"info":{
"eventSource":"",
"sourceType":"I/O",
"status":{
"code":"",
"msg":"",
"msgError":""
},
"transactionId":null,
"traceId":null,
"timestampStart":"2019-05-16T21:30:55.174Z",
"timestampEnd":"2019-05-16T21:30:55.174Z",
"companyIDCode":"",
"channelIDCode":"",
"branchCode":"",
"searchFields":{
"key_3":"value",
"key_2":"value",
"key_1":"value"
},
"annotation":{},
"caller":{
"id":"caller_01",
"version":"1.2.3",
"acronym":""
},
"called":{
"id":"called_id",
"version":"3.2.1",
"acronym":""
},
"storage":{
"id":"",
"start":"",
"end":""
}
}
},
"headers":[],
"payLoad":{
"input":{
"encoding":"1024",
"ccsid":"1024",
"data":"dati_in"
},
"output":{
"encoding":"1024",
"ccsid":"1024",
"data":"dati_out"
}
}
}
';
preg_match_all($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