Hàm mysqli_fetch_fields() trong PHP - PHP Function

$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
	$fieldinfo=mysqli_fetch_fields($result);

	foreach ($fieldinfo as $val){
		printf("Name: %s
",$val->name);
		printf("Table: %s
",$val->table);
		printf("max. Len: %d
",$val->max_length);
	}
	// Free result set
	mysqli_free_result($result);
}

mysqli_close($con);