Class Not Found

Why This Happens

This fatal error occurs when PHP tries to instantiate or reference a class that has not been loaded. Common causes include incorrect namespace declarations, missing use statements, typos in class names, or a misconfigured autoloader that does not map the namespace to the correct directory.

The Problem

// File: src/Controller/UserController.php
namespace App\Controller;

class UserController {
    public function index() {
        $service = new UserService(); // Missing use statement
    }
}

The Fix

namespace App\Controller;

use App\Service\UserService;

class UserController {
    public function index() {
        $service = new UserService();
    }
}

Step-by-Step Fix

1. 1

   Verify the class name and namespace

   Check that the fully qualified class name in the error matches the namespace declaration and class name in the source file.

2. 2

   Check the use statement

   Ensure you have the correct use statement at the top of the file importing the class.

3. 3

   Rebuild the autoloader

   Run composer dump-autoload to regenerate the autoload mappings, and verify composer.json autoload section maps the namespace to the correct directory.