Add exact application files

src/Db.php

@@ -0,0 +1,43 @@
+<?php
+namespace App;
+
+use PDO;
+use PDOException;
+
+class Db
+{
+    // Простая фабрика PDO по логину/паролю MariaDB из сессии
+    public static function connectFromSession(): PDO
+    {
+        if (empty($_SESSION['db_user']) || empty($_SESSION['db_pass'])) {
+            throw new \RuntimeException('Not authenticated');
+        }
+
+        $user = $_SESSION['db_user'];
+        $pass = $_SESSION['db_pass'];
+
+        // TODO: вынести host/port/charset в конфиг .env
+        $dsn = 'mysql:host=localhost;port=3306;charset=utf8mb4';
+
+        $pdo = new PDO($dsn, $user, $pass, [
+            PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
+            PDO::ATTR_EMULATE_PREPARES   => false, // важная настройка [web:28][web:25]
+            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
+        ]);
+
+        return $pdo;
+    }
+
+    public static function testConnection(string $user, string $pass): void
+    {
+        $dsn = 'mysql:host=localhost;port=3306;charset=utf8mb4'; // MariaDB совместим [web:22][web:28]
+        try {
+            new PDO($dsn, $user, $pass, [
+                PDO::ATTR_ERRMODE          => PDO::ERRMODE_EXCEPTION,
+                PDO::ATTR_EMULATE_PREPARES => false,
+            ]);
+        } catch (PDOException $e) {
+            throw new \RuntimeException('Connection failed: ' . $e->getMessage());
+        }
+    }
+}