PHP - Can't create new Google Calendar event using an API Key - php

Question

I'm trying to insert a new event using only an API Key that I created.
The problem is that when I'm just checking available times using FreeBusy, everything works perfectly, but when I try to create and insert a new event, I get the following error:
Uncaught Google_Service_Exception: {
"error": {
"errors": [
{
"domain": "global",
"reason": "required",
"message": "Login Required",
"locationType": "header",
"location": "Authorization"
}
],
"code": 401,
"message": "Login Required"
}
}
In the Authorizing Requests to the Google Calendar API page it is stated that:
Your application must use OAuth 2.0 to authorize requests. No other
authorization protocols are supported. If your application uses Google
Sign-In, some aspects of authorization are handled for you.
But I can't manually authorize access to the calendar every time it is asked for.
How can I authorize requests and insert new events without having to manually authorize them?

Answer 1

You need to use a Service Account, if you want to perform server-to-server API requests. Please see https://developers.google.com/calendar/auth.
Generally you'd create a key, and download the JSON file that is provided. You can then call $client->setAuthConfig($jsonPath); to set up authentication. It's probably a good idea to keep the private key outside of the web root. Then set the scope using $client->addScope('https://www.googleapis.com/auth/calendar'), and instantiate the Calendar service using $service = new Google_Service_Calendar($client);. You should now be able to do your stuff.
You may also need to share the calendar with the generated e-mail address that is associated with the Service Account.