By the time new languages become the new industry standard, most developers will have had plenty of time to learn them. I've never heard of an industry change that happened so fast that it made the majority of working programmers obsolete in 18 months.
In this light, PHP coders are real commodities. They are paid lowly, treated as expendable, and get no respect by peers. I think they're going down the same path of "HTML experts" which were once lucrative business in early 1990s.
Java/C++ programmers fare better because (I guess) there is some fundamental difficulty to be proficient at them. So, despite being old and boring, being good at Java or C(++) is still a good business.
Learning Go/Rust is another way to avoid being a commodity. Although they have a smaller job market, employers need to treat you with respect, because they can't easily find another worker with a matched skill in the market.