I am fetching posts from a public facebook page that has several contributors including myself.
When I use the graph explorer I see all of the posts, but for some reason it strips posts that I personally share when I use the PHP SDK, but includes other peoples' posts.
Here is the graph explorer with all of the posts. The first post is not included in the result set with the PHP SDK. Graph Explorer Link
Did you check the posts across all pages, since there is a pagination? There is a method called getRequestForNextPage() in the FacebookResponse class, which will create the request for the next result set.