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

unset $arr[$key];
开发者_Python百科

Shouldn't it be :

unset($query[$key]);

from the php manual:

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

same with unset.

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

What is the difference between a language construct and a "built-in" function in PHP?

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