I can hire a top-notch PHP engineer for half of what a mid-level JS engineer would be asking.
It's not that PHP engineers are less qualified than JS. I think bootcamps shifted the market for JS developers and now really good engineers cost an arm and a leg while good junior engineers start around the $100k mark. The whole JS salary market is insane and as a startup, I can't afford it right now.
Just pay what good engineers should be paid. If there are PHP developers out there not getting the same salary as a their peers like this post mentions, you should leave that job for a better one. Please demand better, PHP developers, for all of our sakes. Business always wants to put downward pressure on salary and we need to be united against this regardless of preferred tech stacks
I've run no numbers, I have nothing but infrences to base this on, but hiring a mature PHP engineer in Europe would 100% be cheaper in the long run than hiring a junior/mid-level JS engineer anywhere else.