function validate_subject($subject) {

  $errors = [];
  
  // menu_name
  if(is_blank($subject['menu_name'])) {
    $errors[] = "Name cannot be blank.";
  }
  if(!has_length($subject['menu_name'], ['min' => 2, 'max' => 255])) {
    $errors[] = "Name must be between 2 and 255 characters.";
  }

  // position
  // Make sure we are working with an integer
  $postion_int = (int) $subject['position'];
  if($postion_int <= 0) {
    $errors[] = "Position must be greater than zero.";
  }
  if($postion_int > 999) {
    $errors[] = "Position must be less than 999.";
  }

  // visible
  // Make sure we are working with a string
  $visible_str = (string) $subject['visible'];
  if(!has_inclusion_of($visible_str, ["0","1"])) {
    $errors[] = "Visible must be true or false.";
  }

  return $errors;
}