I use stars as a metric in deciding which unfamiliar library seems to be real. It's right up where with number of downloads, and most recent commits. Not a perfect system. Just a sniff test.
It's unbelievable the number and pace of breaking changes.
As an advice, it's less work to disregard the sdk and implement using curl.
Very sloppy and unprofessional from a company that was born, grew and even made their own php.