<?php
function db_connect() {
    static $pdoconn;

    if ($pdoconn) {
        return $pdoconn;
    }

    $config = [
        'host' => '127.0.0.1',
        'dbname' => 'app',
        'user' => 'app',
        'password' => 'app'
    ];

    $dsn = "mysql:host={$config['host']};dbname={$config['dbname']};charset=utf8mb4";
    $options = [
        PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
        PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
        PDO::ATTR_EMULATE_PREPARES => false,
    ];

    try {
        $pdoconn = new PDO($dsn, $config['user'], $config['password'], $options);
        return $pdoconn;
    } catch (PDOException $e) {
        // In a real app, you'd log this error and show a generic message
        throw new PDOException($e->getMessage(), (int)$e->getCode());
    }
}

function run_migrations() {
    $pdo = db_connect();
    $migrationsDir = __DIR__ . '/migrations';
    $files = glob($migrationsDir . '/*.sql');
    sort($files);
    foreach ($files as $file) {
        $sql = file_get_contents($file);
        if ($sql) {
            $pdo->exec($sql);
        }
    }
}