I’m trying to write a tracker for Piwik in my favorite language However I have a hard time understanding how cookies are handled. When I send a tracking request to piwik I only seem to get a cookie identifying the visitor when I enable the use_third_party_id_cookie setting. Is this correct? How should I set the cookie then if Piwik doesn’t give me a visitor id? Create one?
Then, apart from the cookie piwik_visitor = xyz there is the _id query string parameter. What is the difference between the two? Aren’t they the same id?