We currently return php_phongo_bulkwrite_t.commands.len, which is the estimated number of round trips required by a bulk operation. That information is not accessible in libmongoc's public API, and it is also an arbitrary number subject to change (see: CDRIVER-653).

Most users would expect count() to return the number of operations added to the BulkWrite, so we should switch to returning that value.

Note: This will also require a documentation update.