This would be better in Next Generation firewall forum so moved it. hope this correct area.
Stonesoft products are now part of McAfee Next Generation Firewall. This from stonesoft's site.http://www.stonesoft.com/en/
There's no PHP library specifically, though you should be able to GET a fw_cluster or fw_single element to find the information you're looking for (node/cluster status/the status of their interfaces) in JSON or XML, and use PHP's JSON/XML parsers to view those as native PHP arrays.
The examples in the SMC API guide specifically cover retrieving and updating host elements, as they're small and easy to display, but you can retrieve fw_cluster/fw_single elements in the same fashion. Their schema are covered at the Firewall Cluster and Single Firewall pages.