How can the code be modified to display the message only if $_POST["auto"] is either "bmw" or "fiat"?

To achieve this, we can use an if statement to check if the value of $_POST["auto"] is either "bmw" or "fiat" before displaying the message. If the condition is met, then the message will be displayed. Otherwise, the message will not be displayed.

if ($_POST["auto"] == "bmw" || $_POST["auto"] == "fiat") {
    echo "Your selected car is either BMW or Fiat.";
}