Ternary operator with multiple conditions

问题

Hello I am trying to properly format ternary operator to be using multiple conditions in php:

$result = ($var !== 1 || $var !== 2) ? '' : 'default';

The problem is that in this format I always get not true even iv the $var is 1 or 2. With one condition for example $var == 0 it is working fine. Any help will be welcome.

回答1:

This statement will always be true:

($var !== 1 || $var !== 2)

Because $var can never simultaneously be both values, it will always not be at least one of the two values. Which satisfies the || operator.

If you want to know whether $var is one of the two values:

($var === 1 || $var === 2)

If you want to know if $var is neither of the two values, you can negate the condition:

(!($var === 1 || $var === 2))

Or individually negate the operators in the condition and use && instead of || (since all conditions need to be met to prove the negative, instead of just one condition to prove the positive):

($var !== 1 && $var !== 2)

Depending on readability and personal preference.

回答2:

If $var is 0 , $result is "default" but 1 and 2 enter in condition, both are different from both and always enter.

$result = ($var !== 1 && $var !== 2) ? '' : 'default';

来源：https://stackoverflow.com/questions/38128632/ternary-operator-with-multiple-conditions