What's the term for calling a function this way？

Question

unset $arr[$key];

Shouldn't it be :

unset($query[$key]);

Answer 1

If I understand you correctly then it would be called a language construct, such as echo.

http://stackoverflow.com/questions/1180184/what-is-the-difference-between-a-language-construct-and-a-built-in-function-in

Answer 2

from the php manual:

echo is not actually a function (it is a language construct)

same with unset.

Answer 3

isset and unset are actually implemented as PHP unary operators also, so they can be used without parens.