I tried out their PHP SDK, intentionally willing to try out Parse on the backend side of things. I intended to use it as an ORM layer, abstracting out the data

I tried out their PHP SDK, intentionally willing to try out Parse on the backend side of things. I intended to use it as an ORM layer, abstracting out the data structures. However, my experience was that making multiple queries (even 3-4) would make the app appear slow. This is in no way a fault of Parse, just how it is. So, I'd recommend using Parse with any of the frontend SDKs (JS/Android/iOS), but would warn you against trying it on the backend side of things (where PHP is the only offering so far).