PHP mysqli_next_result() Function

<?php
$con=mysqli_connect("localhost","my_user","my_password","my_db");
// Check connection
if (mysqli_connect_errno())
  {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
  }

$sql = "SELECT Lastname FROM Persons ORDER BY LastName;";
$sql .= "SELECT Country FROM Customers";

// Execute multi query
if (mysqli_multi_query($con,$sql))
{
  do
    {
    // Store first result set
    if ($result=mysqli_store_result($con))
      {
      while ($row=mysqli_fetch_row($result))
        {
        printf("%s\n",$row[0]);
        }
      mysqli_free_result($con);
      }
    }
  while (mysqli_next_result($con));
}

mysqli_close($con);
?>