Facebook Graph API Data Incorrect

Question

Small problem here. I have an event created on Facebook and am using the Graph API to get the number of attendees.

I get the list of attendees with PHP from https://graph.facebook.com/EVENTID/attending?access_token=TOKENHERE and it returns a list of names.

However, the number of attendees is about 6 people lower than what is shown on the Facebook event page. Why would these numbers not match? Is there something in particular I'm supposed to do in the code to get the entire list?

Answer 1

As answered in the comments:

This discrepancy is probably down to a number of the attendees having opted out of Facebook Platform, which means their data isn't passed to apps via the API. Can't be 100% sure without the Event ID, but its a likely reason. – Simon Cross

Answer 2

From the Graph API, the people who have not joined the event will not show up under /{eventid}/attending, you need to add in the users who are returned in /{eventid}/not_replied. The not_replied set seems to be a special set in the GraphAPI.. and if you look at the docs, there is a mention of only people who have joined the event.