Not a PHP guru here but reversing the flow control might help you google up the details.
Contracts don't interact with other systems in either direction. Ever.
The most interaction that can take place is
- Alice signed a transaction with data and/or ether and sent it to the contract, or
- Alice listens to events emitted by the contract.
There are some experimental PHP Web3 implementations.
Main takeaway - the contract just does its thing. The server can react by observing it (Pull) but never by anything on the Ethereum side interacting with the server (Push).
Hope it helps.