Using Options with filter_var()

<?php
$message = "";
$month_error = "";
$day_error = "";
$year_error = "";

// Create variables for range of options
$month_options = ["options" => ["min_range" => 1, "max_range" => 12]];
$day_options = ["options" => ["min_range" => 1, "max_range" => 31]];
$year_options = ["options" => ["min_range" => 1903, "max_range" => 2021]];


// create function to validate user input based on each input option range
function validateInput($type, &$error, $options_arr){
  if (!filter_var($_POST[$type], FILTER_VALIDATE_INT, $options_arr)){
    $error = "* Invalid ${type}";
    return FALSE;
  } else {
    return TRUE;
  }
}

  if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $test_month = validateInput("month", $month_error, $month_options);
    $test_day = validateInput("day", $day_error, $day_options);
    $test_year = validateInput("year", $year_error, $year_options);
    if ($test_month && $test_day && $test_year){
      $message = "Your birthday is: {$_POST["month"]}/{$_POST["day"]}/{$_POST["year"]}";
    }
  }

?>

<form method="post" action="">
    Enter your birthday:
    <br>
    Month: <input type="number" name="month" value="<?= $_POST["month"];?>">
    <span class="error"><?= $month_error;?>     </span>
  <br>
    Day: <input type="number" name="day" value="<?= $_POST["day"];?>">
  <span class="error"><?= $day_error;?>     </span>
    <br>
    Year: <input type="number" name="year" value="<?= $_POST["year"];?>">
    <span class="error"><?= $year_error;?>      </span>
    <br>
    <input type="submit" value="Submit">
</form>
    <p><?= $message;?></p>