DB connect

<?php

class DB
{
    private $link;

    public function __construct()
    {
        $this->connect();
    }

    private function connect()
    {
        $config = require_once 'config.php';

        $dsn = 'mysql:host=' . $config['host'] . ';dbname=' . $config['db_name'] . ';charset =' . $config['charset'];

        $this->link = new PDO($dsn, $config['username'], $config['password']);

        return $this;
    }

    public function execute($sql)
    {
        $sth = $this->link->prepare($sql);

        return $sth->execute();
    }

    public function query($sql)
    {
        $exe = $this->execute($sql);

        $result = $exe->fetchAll(PDO::FETCH_ASSOC);

        if ($result == false) {
            return [];
        }
        return $result;
    }
}

$db = new DB();

$db->execute("INSERT INTO charz SET name='MadDog', health='100'");