<p>I have a website where clients pay for a service but have to out the money upfront via escrow, I'm very proficient with PHP (this is what the website is coded in) how would I go about implementing an escrow system that would work automatically?</p>

You need to break down your design into components and think about the process.
Escrow works like this:
Entity A deposits money into Escrow Account for Entity B.
Entity A and Entity B come to an agreement
The Escrow account is deposited to Entity B.
Implementation wise, I'd track escrow deposits like any transaction, I'd also track escrow payments the same way.
You need to come up with a way to store "Work Orders" in a database. These would have two columns "AcceptedByA", and "AcceptedByB", as well as the amount of money.
The process would be:
Entity A opens a workorder and pays $X into the Escrow Account
Entity B does whatever the workorder requires (Setting AcceptedByB to true)
Entity A sets "AcceptedByA" to true.
A transaction runs to pay EntityB from the Escrow Account.
This is extremely high level, but its a rather simple idea.