问PHP RestAPI MySQL数据库多个连接

EN

<?php
class DbHandler
{
    private $conn;
    function __construct()
    {
        require_once dirname(__FILE__) . '/db_connect.php';
        $db         = new DbConnect();
        $this->conn = $db->connect();
    }

    public function getSpotlight($user_id) {
      $stmt = $this->conn->prepare("SELECT *, (SELECT COUNT(*) FROM followers WHERE following = u.id) as followers, (SELECT COUNT(*) FROM posts WHERE user_id = u.id) as totalPosts from users u WHERE u.id NOT IN (select if(user_id = :var1, user_with, user_id) from friends where user_id = :var1 OR user_with = :var1) AND u.id != :var1 order by followers desc limit 10;");
      $stmt->bindParam(":var1", $user_id);
      $stmt->execute();
      $users = $stmt;
      $stmt  = null;
      return $users;
    }

<?php
class DbConnect
{
    private $conn;
    function __construct()
    {
    }

    function connect()
    {
        include_once dirname(__FILE__) . '/config.php';
        $host       = DB_HOST;
        $db_name    = DB_NAME;
        $user       = DB_USERNAME;
        $pass       = DB_PASSWORD;
        $this->conn = new PDO("mysql:host=$host;dbname=$db_name", $user, $pass);
        if (mysqli_connect_errno()) {
            echo "Failed to connect to MySQL: " . mysqli_connect_error();
        }
        return $this->conn;
    }
}
?>