This ... isn't even something I ever considered. Back when I was learning programming we had these things called BOOKS, and in those books were all we ever really needed to know the ins and outs of a language.
But that was a different age, where you'd buy a Borland or Microsoft compiler and get a stack of four to six books of 200+ pages each with it. Even in the early days with ROM Basic you got a manual that gave a detailed reference of every command, an overview of the language syntax, and so forth WITH the computer or language so you never really needed a third party book on the topic. In fact Commodore and TRS-80's BASIC language guides were so simple even toddlers could grasp it.
... and who needs to write down notes when you have a clear concise reference that came with it?
Now though? Well, with PHP I don't really see the need since php.net has its own search, I use MDN as my JavaScript reference, and any other language typically has a website that gives me at LEAST a proper function/method reference.
You need a reference, we have the Internet.