Toggling true/false variables

Alan @ CIT · 03-13-2008, 11:43 PM

Hi all,

Just a quick tip for you all

I'm sure that we've all used something like the following before to toggle a bool variable:

PHP Code:


			
if ($myVar == true)

{

    $myVar = false;

}

else

{

    $myVar = true;

}

Well you'll be please to know that there is a shorter way of doing it

PHP Code:


			
$myVar ^= true;

This does exactly the same as our if() block above - if $myVar is false, it sets it to true. If it is true, it sets it to false.

Hopefully usefull to someone

Alan

wGEric · 03-14-2008, 12:56 AM

I haven't tried this but it seems like the following would work as well. It's a little easier to understand.

PHP Code:


			
$var = !$var;

DeMo · 03-14-2008, 01:06 AM

I've always done it the way Eric showed.

Salathe · 03-14-2008, 01:23 AM

What you're doing there is utilizing the bitwise 'xor' operator. It's a little bit in depth to explain this operation in detail so we'll go with "it just works"... sort of. Since we're only working with one bit (0 or 1) the expression works something like:

PHP Code:


			
$myVar = FALSE; // (bool) false

$myVar ^= TRUE; // (int) 1

$myVar ^= TRUE; // (int) 0

$myVar ^= TRUE; // (int) 1

So, really we're making FALSE into (int) 1, or TRUE into (int) 0 rather than strictly converting between TRUE/FALSE. An alternative (which actually preserves boolean type) would be to go along the lines of:

PHP Code:


			
$myVar = FALSE;   // (bool) false

$myVar = !$myVar; // (bool) true

$myVar = !$myVar; // (bool) false

$myVar = !$myVar; // (bool) true

As mentioned above, it keeps the boolean type rather than giving integer results and is also, for me at least, more logical (pardon the pun) in that we're saying (if $myVar is originally true) "$myVar equals not $myVar" => "$myVar equals not true" => "$myVar equals false".