The core language itself and stdlibs, sure, it'd take just several dozen hours to pick it up. That goes for any high-level, C-family programming language around today, really. Can you do that and be nearly as productive in PHP (or any other language) as you are in your current daily use language? No: you need to invest in learning common design patterns, the library ecosystem, and tooling in order to be productive at a high professional level, and that is a task that takes longer and arguably never even really ends. Putting down real roots in a programming language is a large investment.