PHP mysqli_fetch_field() 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,Age FROM Persons ORDER BY Lastname";

if ($result=mysqli_query($con,$sql))
  {
  // Get field information for all fields
  while ($fieldinfo=mysqli_fetch_field($result))
    {
    printf("Name: %s\n",$fieldinfo->name);
    printf("Table: %s\n",$fieldinfo->table);
    printf("max. Len: %d\n",$fieldinfo->max_length);
    }
  // Free result set
  mysqli_free_result($result);
}

mysqli_close($con);
?>