[masklinn]

"Implicit reference semantics" = everything (or near enough) is implicitly a reference. That's what you get in Python, Ruby, or Javascript: when you pass something around, you're really passing a reference to it, a pointer. Everyone ends up referring to the same thing, and sharing it.

"Value semantics": you pass the value itself around, which means you're shallow-copying it all the time. That's what you get when you pass or return a bare non-interface type in Go.

PHP is a bit of a mess, objects are passed by reference (= implicit reference semantics) but arrays are passed by value, and you can opt them into pass-by-reference. You can also pass non-arrays by reference, though I don't think that's very common.