There are no PHP nodes in FF Pro -- there's no PHP anywhere in fact, as our system doesn't use that programming language anymore.
Because FF Pro is a SaaS, we can't add the ability for users to run code on our infrastructure like this as its a large security risk that also puts us at risk of users run malicious code, which can then impact all customers (imagine if Google wanted to shut down our servers because of complaints from some ISP/watchdog).
However, we are working on smart rotators and logic nodes which will add a lot of capabilities., including dynamic rotation based on performance.