View file app\Core\Session.php

<?php

namespace App\Core;

class Session
{
    public static function start(): void
    {
        if (session_status() === PHP_SESSION_NONE) {
            session_start();
        }
    }

    public static function set(string $key, $value): void { $_SESSION[$key] = $value; }
    public static function get(string $key, $default = null) { return $_SESSION[$key] ?? $default; }
    public static function has(string $key): bool { return isset($_SESSION[$key]); }
    public static function remove(string $key): void { unset($_SESSION[$key]); }
    public static function flash(string $key, $value = null)
    {
        if ($value !== null) {
            $_SESSION['_flash'][$key] = $value;
        } else {
            $val = $_SESSION['_flash'][$key] ?? null;
            unset($_SESSION['_flash'][$key]);
            return $val;
        }
    }

    public static function destroy(): void
    {
        $_SESSION = [];
        session_destroy();
    }
}