Hàm mysqli_fetch_lengths() 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 * FROM Persons ORDER BY Lastname";

if ($result=mysqli_query($con,$sql)){
	$row=mysqli_fetch_row($result);

	// Display field lengths
	foreach (mysqli_fetch_lengths($result) as $i=>$val){
	    printf("Field %2d has length: %2d
",$i+1,$val);
	}

	// Free result set
	mysqli_free_result($result);
}

mysqli_close($con);