Composer, php-diff and Class Not Found problems

Hoping someone can point out the error of my ways. Haven't used composer very much, but it appears to have properly loaded the files, but I am still getting the dreaded "Class "DiffHelper" not found" error.
1) Installed the library with composer: "composer require jfcherng/php-diff"
2) Verified the files are there (/_site/vendor/jfcherng/php-diff/src/DiffHelper.php)
3) Added to the top of my controller: "use Jfcherng\Diff\DiffHelper;" (also tried "use DiffHelper;")
4) In my view file called: 

PHP Code:

<?php
 $changes = DiffHelper::calculate($oldRecord[0]['comments'], $oldRecord[count($oldRecord)-1]['comments'], 'Unified');
 echo $changes;
 ?>

Ran the page and got the "Class not found" error! Feeling like I missed a step somewhere.

Thanks in advance!

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)

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?