Question

I need to check to make sure a variable equals either 5, 10, 50 or 100. If it doesn’t then I want to set it to 5. Can someone tell me what’s wrong with this IF statement?

if (isset($_REQUEST['number']) && $_REQUEST['number'] !== "5" || $_REQUEST['number'] !== "10" || $_REQUEST['number'] !== "50" || $_REQUEST['number'] !== "100") {
  $number = 5;
} else {
  $number = $_REQUEST['number'];
}

Answer 1

You need to break up your logic to overcome operator precedence. When in doubt, use parenthesis.

I also inverted the logic. It reads more naturally.

if (isset($_REQUEST['number']) && ($_REQUEST['number'] == "5" || $_REQUEST['number'] == "10" || $_REQUEST['number'] == "50" || $_REQUEST['number'] == "100")) {
  $number = $_REQUEST['number'];
} else {
  $number = 5;
}

While the above works, you could also streamline it with something like in_array().

isset($_REQUEST['number']) && in_array($_REQUEST['number'], array(5, 10, 50, 100))