在php中自动关闭数据库连接?

我的 config.php 文件中有我的一个网络应用程序.

I have following in my config.php file for one of my web app.

//db settings
    $host = 'localhost'; //database location
    $user = 'example'; //database username
    $pass = 'example12'; //database password
    $db_name = 'example'; //database name

//create db connection
    $link = mysql_connect($host, $user, $pass);
    mysql_select_db($db_name);

//sets encoding to utf8
    mysql_query("SET NAMES utf8");

我将 config.php 包含在我应用程序的所有页面顶部(代码的第一行).

I am including config.php in all pages of my application at top (1st line of code).

我想知道 PHP/MYSQL 会自动保持连接打开和关闭还是我需要显式调用它们.连接正在自行打开，因为我正在正确执行所有基于数据库的任务.但不要在任何地方关闭连接，这是一个高流量网站.

I want to know that will PHP/MYSQL maintain connection open and close automatically or I need to explicitly call them. Connection is opening by itself, as I am doing all db based tasks properly. But not closing connection anywhere, this is a high traffic website.

如有不对之处请指正.

谢谢！