$correctusername = array('user1','user2','user3');
$correctpassword = array('password1','password2','password3');
if(($username == $correctusername['0'])&&($password == $correctpassword['0'])){
header ('location: valuable.html');
} elseif(($username == $correctusername['1'])&&($password == $correctpassword['1'])){
header ('location: valuable.html');
} elseif(($username == $correctusername['2'])&&($password == $correctpassword['2'])){
header ('location: valuable.html');
} else {
echo "Incorect Username/Password.";
}