Composer Autoload File Not Found

Why This Happens

Most PHP projects use Composer for dependency management and autoloading. The vendor/autoload.php file is generated by Composer and loads all dependencies and PSR-4 autoloaded classes. If this file is missing, no dependencies or autoloaded classes will be available.

The Problem

// vendor directory does not exist
require __DIR__ . '/vendor/autoload.php';

The Fix

// First run: composer install
// Then in your PHP file:
require __DIR__ . '/vendor/autoload.php';

Step-by-Step Fix

1. 1

   Run composer install

   Execute composer install in the project root to download dependencies and generate the autoloader.

2. 2

   Check the path

   Verify the path to vendor/autoload.php is correct relative to your entry point script. Use __DIR__ for reliable paths.

3. 3

   Check composer.json exists

   Ensure the project has a composer.json file. If not, initialize one with composer init.