Composer, php-diff and Class Not Found problems

I tried installing this package. There were no problems.

Check it out.
- Use section must be specified after namespace
- file vendor/composer/autoload_psr4.php should contain an entry about the path to the package. (if not, use `composer dump-autoload` command)

The "Use" is after the namespace:

PHP Code:

<?php

namespace App\Controllers\Auction;

use App\Entities\User;

use DiffHelper; 


The psr4 file contains:

Code:

    'Jfcherng\\Utility\\' => array($vendorDir . '/jfcherng/php-color-output/src', $vendorDir . '/jfcherng/php-mb-string/src'),
    'Jfcherng\\Diff\\' => array($vendorDir . '/jfcherng/php-diff/src', $vendorDir . '/jfcherng/php-sequence-matcher/src'),

I think I am giving up on this. I found a javascript from google that does the same thing with zero hassle. Thanks for checking it out, but it just shouldn't be this difficult! LOL. Isn't that the point of composer?

Were the steps I used correct?