Double not (!!) operator in PHP

Question

What does the double not operator do in PHP?

For example:

return !! $row;

What would the code above do?

Answer 1

Lets look at

!$a;

Rather than interpreting the ! operator as as taking the

Boolean opposite of the value to its right

read

take the Boolean opposite of the expression to its right

In this case

$a;

could be an expression

so to is

!$a;

so is

!!$a;

and

!!!$a;

and so on, as each of these is a valid expression, the ! operator can be prepended to each of them.