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phpxorboolean-logicboolean-operations

Make sure exactly one boolean of a given list is true?

If I have the following booleans

const YESTERDAY = false;
const TODAY = true;
const TOMORROW = false;

What code can I write to make sure exactly one is true?

I've tried this:

$x = self::YESTERDAY ^ self::TODAY ^ self::TOMORROW;

The problem is that with all three constants set to true then $x is true.

Solution

  • $x = ((int) self::YESTERDAY) + ((int) self::TODAY) + ((int) self::TOMORROW); Then if $x === 1; You've got what you need.

    EDITED:

    Even without type casts (int), it works well, thanks to @DaveRandom, so:

    if (self::YESTERDAY + self::TODAY + self::TOMORROW == 1) {}, as for me.