PHP mysqli_free_result() and mysqli_fetch_array() functions

mysql_free_result() only needs to be called when considering how much memory it will take up when returning a very large result set. All associated memory will be automatically released after the script ends.

After we execute the SELECT statement, it is a good habit to release the cursor memory. . Memory release can be achieved through the PHP function mysql_free_result().

//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);

Note: In addition to talking about mysqli_free_result, I also want to mention the second parameter of the mysqli_fetch_array() function

mysqli_fetch_array(result,resulttype)
resulttype parameter:
1: MYSQLI_ASSOC. The returned result array is an associative array. The key of the array is the corresponding field name. You can use it like this:
row[′firstname′], row['lastname']…..

2: MYSQLI_NUM. The returned result array is an index array. The keys of the array are numeric indexes such as 0,1,2,3,4. You can only use it like this:
$row[0], row[1] …..

3: MYSQLI_BOTH, there are both field index and numeric index in the returned result array. When you use it, both of the above can be used.

Reference reading: http://www.manongjc.com/article/1191.html