System Architecture

<?php
// 1. Load configuration
require_once 'Config/Conexion.php';

// 2. Start session
if (session_status() === PHP_SESSION_NONE) session_start();

// 3. Determine requested URL
$url = isset($_GET['url']) ? $_GET['url'] : '';

if (empty($url)) {
    if (isset($_SESSION['logged_in']) && $_SESSION['logged_in'] === true) {
        // Redirect to dashboard if logged in
    }
}

// 4. Parse URL and route request
$urlParts = explode('/', rtrim($url, '/'));
$controllerName = ucfirst($urlParts[0]) . 'Controller';
$method = isset($urlParts[1]) ? $urlParts[1] : 'index';

// 5. Execute controller method
$controllerPath = 'Controllers/' . $controllerName . '.php';

if (file_exists($controllerPath)) {
    require_once $controllerPath;
    if (class_exists($controllerName)) {
        $controller = new $controllerName();
        if (method_exists($controller, $method)) {
            $controller->{$method}();
        } else {
            die("Error: Method '$method' does not exist.");
        }
    }
} else {
    die("Error: Controller '$controllerName' not found.");
}

private function getRedirectUrl($grado) {
    switch ($grado) {
        case 1: 
            // Administrator - Full access
            return 'index.php?url=home/index'; 
        case 2: 
            // Auxiliary - Create deviations
            return 'index.php?url=devolucion/crear'; 
        case 3: 
            // Consultant - Read-only access
            return 'index.php?url=consulta/index';
        default: 
            return 'index.php?url=auth/index';
    }
}

<?php
class Conexion {
    public static function Conectar() {
        // Database credentials
        $host = '192.200.100.40';
        $db   = 'devolutionsync';
        $user = 'SANMARINO';
        $pass = 'sanmarino2021*';
        $charset = 'utf8';

        // Connection string
        $dsn = "mysql:host=$host;dbname=$db;charset=$charset";

        $opciones = [
            PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
            PDO::ATTR_EMULATE_PREPARES   => false,
        ];

        try {
            $pdo = new PDO($dsn, $user, $pass, $opciones);
            return $pdo;
        } catch (PDOException $e) {
            die("Connection error (PDO): " . $e->getMessage());
        }
    }
}

public function guardar($datos) {
    $sql = "INSERT INTO devoluciones (
                nit, nombre_cliente, direccion, item_producto, descripcion_producto, 
                unidad, kg, motivo, cantidad_und, cantidad_kg, 
                observacion, usuario_creador, estado, fecha_creacion, evidencia
            ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, 'Pendiente', NOW(), ?)";
    
    $stmt = $this->db->prepare($sql);
    
    return $stmt->execute([
        // ... other parameters ...
        $datos['evidencia'] ?? null // Handle null if no evidence
    ]);
}

public function revisar() {
    if ($_SERVER['REQUEST_METHOD'] === 'POST') {
        try {
            // Validate received data
            $id = intval($_POST['id_devolucion'] ?? 0);
            $accion = trim($_POST['accion'] ?? '');
            
            if ($id <= 0) {
                throw new Exception('Invalid deviation ID');
            }
            
            if (!in_array($accion, ['aprobado', 'rechazado'])) {
                throw new Exception('Invalid action');
            }
            
            // Process review
            $resultado = $this->model->procesarRevision($id, $accion, $codigo, $obs, $revisor);
            
            if ($resultado) {
                header('Location: index.php?url=admin/index&msg=success');
            } else {
                throw new Exception('Database error processing review');
            }
            
        } catch (Exception $e) {
            error_log("Error in AdminController::revisar - " . $e->getMessage());
            header('Location: index.php?url=admin/index&msg=error');
        }
        exit;
    }
}