My apologies, "functionality" isn't a very precise word in this case. I meant it in terms of what functionality is in the language's syntax. For instance, Lisp has macros whilst PHP does not. And whilst later versions of PHP do support things like first class functions, they do so in an unwieldy and verbose fashion that negates a lot of their advantages:
#(* n %)
(* n _)
(* n)
function($x) use ($n) { return $n * $x; }
