Google Calendar API - can only update event once

Question

I've encountered the same problem as described in this post:

Google Calendar api v3 re-update issue

Namely, once I create an event and update it once using the Google Calendar API (v3), I am no longer able to update the event. When I attempt to, I get a 400 - Invalid value response. (FWIW I'm working in PHP).

Following a lead offered in the post I referenced above, I attempted to solve the issue using etags (though admittedly my grasp of how they work is limited). Basically, on event update, the API returns an etag in its response, which I now save in my database. Then for subsequent (n > 1) updates, I pull the current etag from the database and include it in the http header:

Content-Type:  application/json
Authorization:  OAuth [token]
If-Match: [etag]

This follows info under the "Updating Entries" header here: http://code.google.com/apis/gdata/docs/2.0/reference.html#ResourceVersioning

Sidenote: in the google ref above, the If-Match header is shown as

If-Match: "S0wCTlpIIip7ImA0X0QI"

with double quotes around the etag. I'm saving the etags in the database with double quotes, exactly as I receive them in first update response. Do I need to escape the quotes or anything when adding to the header using curl_setopt/HTTPHEADER?

Despite implementing this etag If-Match thing, I'm still getting the same 400 - Invalid value response. I know that my request bodies are valid because the first update works fine. There's just some additional issue surrounding subsequent updates.

Any help much appreciated.

Answer 1

Make sure to increment the sequence number field when updating events.