proč funkce nevidí připojení k databázi

$mysqli = mysqli_connect("localhost","root","","people");
  mysqli_set_charset($mysqli,"utf8");
  
  function enumDropdown($table_name, $column_name)
        {   
           $result = $mysqli->query("SELECT COLUMN_TYPE FROM INFORMATION_SCHEMA.COLUMNS  //zde funkce nezná $mysqli
               WHERE TABLE_NAME = '$table_name' AND COLUMN_NAME = '$column_name'")
           or die ($mysqli->error());
            $row = mysqli_fetch_array($result);
    }