AppWarpS2 is writtten in Java and can be deployed over GPaaS or any 3rd party IaaS provider. You can integrate App42 Client side Java SDK to your AppWarpS2 server project to use its available module.
For PHP code, you can deploy your PHP code on any server and call its REST based APIs from AppWarpS2 server.
For storing data, you can use App42 Cloud APIs on your AppWarpS2 server. You can also access your private database through REST based calls from AppWarpS2 server.
Please let me know if you have any further queries.