PHP mysqli_free_result()與mysqli_fetch_array()函數

//定义头文件，字符格式
 header("Content-type:text/html;charset=utf-8");
 error_reporting(ERR_ALL & ~ E_NOTICE); 

 //定义本地服务器连接信息
 $servername="localhost";
 $username="root";
 $password="admin";
 $dbname="test";

 //本地连接
 $conn=mysqli_connect($servername,$username,$password,$dbname)or die(mysqli_error());

//要查询的信息
$sql="SELECT firstname,lastname,email FROM hello";
$result=mysqli_query($conn,$sql);

//判断字符串是否执行成功
if($result){
 while($row=mysqli_fetch_array($result,MYSQLI_ASSOC))  {
    echo $row["firstname"]." ".$row["lastname"]." ".$row["email"]."<br>";
    echo "<hr>";
  }
}else{
  die("fetch data failed!");
}

//释放游标内存
mysqli_free_result($result); 
//关闭数据库连接
mysqli_close($conn);