Question

<?php

$param = 'c';

if ($param != 'a' || $param != 'b') 
{
    echo 'Param != a OR b';
}else
{
    echo 'Param = a OR b';
}

?>

The if statement above does not work as expected because the if will ALWAYS evaluate to TRUE regardless of the value of $param.

Is there another way to construct the if statement that will work as expected (keeping the original intention… i.e. $param not being equal to a or b)?

Answer 1

According to De Morgan’s laws:

!(A OR B) = !A AND !B
!(A AND B) = !A OR !B

In your case, you have to replace the || with the && operator.