шаг 1 сделан

app/Core/Database.php

@@ -0,0 +1,36 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Core;
+
+use PDO;
+
+final class Database
+{
+    private static ?PDO $pdo = null;
+
+    public static function pdo(): PDO
+    {
+        if (self::$pdo !== null) {
+            return self::$pdo;
+        }
+
+        $host = app_env('DB_HOST', 'localhost');
+        $port = app_env('DB_PORT', '3306');
+        $database = app_env('DB_DATABASE', '');
+        $charset = app_env('DB_CHARSET', 'utf8mb4');
+        $username = app_env('DB_USERNAME', '');
+        $password = app_env('DB_PASSWORD', '');
+
+        $dsn = "mysql:host={$host};port={$port};dbname={$database};charset={$charset}";
+
+        self::$pdo = new PDO($dsn, $username, $password, [
+            PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
+            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
+            PDO::ATTR_EMULATE_PREPARES => false,
+        ]);
+
+        return self::$pdo;
+    }
+}