practice_mvc/config/DBconnect.php

<?php

namespace App\Repository;

use PDO;
use PDOException;

class Singleton
{
    private static $instance;
    private $login = 'root';
    private $pass = '';
    private $dbname = 'school';
    private $host = '127.0.0.1';
    private $charset = 'utf8';
    public $pdo;

    public static function getInstance()
    {
        if (null === self::$instance) {
            self::$instance = new self();
        }
        return self::$instance;
    }

    private function __construct()
    {
        $dsn = "mysql:host={$this->host};dbname={$this->dbname};charset={$this->charset}";
        $opt = [
            PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
            PDO::ATTR_EMULATE_PREPARES => false,
        ];
        try {
            $this->pdo = new PDO($dsn, $this->login, $this->pass, $opt);
        } catch (PDOException $e) {
            die('Подключение не удалось: ' . $e->getMessage());
        }
    }

    private function __clone()
    {
    }

}