"...after years of using it I rarely have to check the documentation for function behavior (such as array_merge)."
This should not be something that takes years. I rarely have to check the documentation for similar Ruby functions after using it for only a couple months. After using PHP for 8 months straight, all day every day, I still had to look up almost every standard library function call - even if I thought I knew how it worked, I still had to check because the pervasive inconsistencies in the standard library ensured that I could never be confident in my guess.
(This is only the tip of the iceberg for why I don't like PHP and don't recommend people use it, for other reasons see: fatal errors vs. exceptions, the strange implementation of OOP (late static binding? isn't that an oxymoron?), and the numerous failing test cases / bugs that reveal themselves in every new release.)
This should not be something that takes years. I rarely have to check the documentation for similar Ruby functions after using it for only a couple months. After using PHP for 8 months straight, all day every day, I still had to look up almost every standard library function call - even if I thought I knew how it worked, I still had to check because the pervasive inconsistencies in the standard library ensured that I could never be confident in my guess.
(This is only the tip of the iceberg for why I don't like PHP and don't recommend people use it, for other reasons see: fatal errors vs. exceptions, the strange implementation of OOP (late static binding? isn't that an oxymoron?), and the numerous failing test cases / bugs that reveal themselves in every new release.)