Double not (!!) operator in PHP

php operators
Andrei picture Andrei · Jan 24, 2010 · Viewed 40.8k times · Source

What does the double not operator do in PHP?

For example:

return !! $row;

What would the code above do?

Answer

Theo picture Theo · Jan 24, 2010

It's not the "double not operator", it's the not operator applied twice. The right ! will result in a boolean, regardless of the operand. Then the left ! will negate that boolean.

This means that for any true value (numbers other than zero, non-empty strings and arrays, etc.) you will get the boolean value TRUE, and for any false value (0, 0.0, NULL, empty strings or empty arrays) you will get the boolean value FALSE.

It is functionally equivalent to a cast to boolean:

return (bool)$row;

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