如何调整PHP商城开发中的数据库连接？

// 数据库主机名
$servername = "localhost";

// 数据库用户名
$username = "root";

// 数据库密码
$passWord = "";

// 数据库名称
$dbname = "shop";

// 创建连接
$conn = Mysqli_connect($servername, $username, $password, $dbname);

// 设置字符集
mysqli_set_charset($conn, 'utf8');

$conn = new mysqli($servername, $username, $password, $dbname);

if ($conn->connect_error) {

    die("连接失败: " . $conn->connect_error);
}

if (!$conn->set_charset("utf8")) {

    die("设置字符集失败: " . $conn->error);
}

$pool = new SwooleCoroutineChannel(10);

//线程启动时，初始化N个MySQL连接并放入到池中
for ($i = 0; $i < 10; $i++) {
    $conn = new mysqli($servername, $username, $password, $dbname);
    if ($conn->connect_errno) {
        throw new RuntimeException($conn->connect_error);
    }
    
    $pool->push($conn);
}

//从连接池中借用一个MySQL连接对象
$conn = $pool->pop();

//使用连接对象执行SQL语句
$retval = $conn->query($sql);

//SQL操作完成后将连接对象归还给连接池
$pool->push($conn);