Google analytics api v4 custom report - php

Question

I'm trying to automatise the Google analytics report of our app websites, something like 55 or so.
What I need is:
avg time
users new/returning
direct/referral/search
users per day (based on 1st of the month to the last day)
I'm using the guide from Google
https://developers.google.com/analytics/devguides/reporting/core/v4/quickstart/web-php
my function for the report is something like this:
function getReport($analytics) {
// Replace with your view ID, for example XXXX.
$VIEW_ID = "XXXX";
// Create the DateRange object.
$dateRange = new Google_Service_AnalyticsReporting_DateRange();
$dateRange->setStartDate("2019-05-01");
$dateRange->setEndDate("2019-05-31");
// Create the Metrics object.
$sessions = new Google_Service_AnalyticsReporting_Metric();
$sessions->setExpression("ga:sessions");
$sessions->setAlias("sessions");
$users = new Google_Service_AnalyticsReporting_Metric();
$users->setExpression("ga:users");
$users->setAlias("users");
$newSessions = new Google_Service_AnalyticsReporting_Metric();
$newSessions->setExpression("ga:percentNewSessions");
$newSessions->setAlias("newSessions");
// Create the ReportRequest object.
$request = new Google_Service_AnalyticsReporting_ReportRequest();
$request->setViewId($VIEW_ID);
$request->setDateRanges($dateRange);
$request->setMetrics(array($sessions,$users,$newSessions));
$body = new Google_Service_AnalyticsReporting_GetReportsRequest();
$body->setReportRequests( array( $request) );
return $analytics->reports->batchGet( $body );
}
Of course is not the definitely one I'm just experimenting with some metrics.
I was trying to get back the users per day like this
$monthusers = new Google_Service_AnalyticsReporting_Metric();
$monthusers->setExpression("ga:30dayUsers");
$monthusers->setAlias("monthusers");
and then in the request
$request->setMetrics(array($sessions,$users,$newSessions,$monthusers));
but it throw a 500 error, any idea on how to get back the users per day? and based on the:
$dateRange->setStartDate("2019-05-01");
$dateRange->setEndDate("2019-05-31");

Answer 1

As per mentioned in the Dimensions & Metrics Explorer for the metric "ga:30dayUsers":
At least one of ga:nthDay, ga:date, or ga:day must be specified as a
dimension to query this metric.
You could use the ga:day dimension into your report request to solve the issue:
$day = new Google_Service_AnalyticsReporting_Dimension();
$day->setName("ga:day");
$request->setDimensions(array($day));