Smart loader for libraries in WordPress

smart-loader.php

<?php

use PPWPProPluginsAds\Autoloader;

if (file_exists(__DIR__ . '/vendor')) {
    require_once __DIR__ . '/vendor/autoload.php';
}

$version = '0.1.0';

if (!function_exists('calculatePriorityFromVersion')) {
    /**
     * This function requires the version in a semantic version format: 0.0.0(-[alpha|beta|rc].0)?
     *
     * Examples:
     *
     * 1.2.3-alpha.4 => 01 02 03 1 04 => 10,203,104
     * 10.20.30-alpha.40 => 10 20 30 1 40 => 102,030,140
     * 10.20.30-beta.40 => 10 20 30 1 40 => 102,030,240
     *
     * @see http://semver.org/
     *
     * @param string $version
     *
     * @return int
     */
    function calculatePriorityFromVersion($version)
    {
        $priority = 0;

        if (strpos($version, '-')) {
            // Has unstable version
            $parts            = explode('-', $version);
            $version          = $parts[0];
            $unstableVersion  = strtolower($parts[1]);
            $unstablePriority = 0;

            if (false !== strpos($unstableVersion, 'alpha')) {
                $unstablePriority += 100;
            } elseif (false !== strpos($unstableVersion, 'beta')) {
                $unstablePriority += 200;
            } elseif (false !== strpos($unstableVersion, 'rc')) {
                $unstablePriority += 300;
            }

            $unstableVersion = preg_replace('/(alpha|beta|rc)\./', '', $unstableVersion);

            $unstablePriority += (int)$unstableVersion;

            $priority += $unstablePriority;
        }

        $versions = explode('.', $version);

        $priority += (int)$versions[0] * 10000000;
        $priority += (int)$versions[1] * 100000;
        $priority += (int)$versions[2] * 1000;

        return $priority;
    }
}

$loadingPriority = PHP_INT_MAX - calculatePriorityFromVersion($version);

add_action('ppwppropluginsads_library_load', function () use ($version) {
    if (!defined('PPWPPROPLUGINSADS_LOADED')) {
        define('PPWPPROPLUGINSADS_VERSION', $version);

        if (!class_exists('PPWPProPluginsAds\\Autoloader')) {
            require_once __DIR__ . '/core/Autoloader.php';
        }

        Autoloader::register('PPWPProPluginsAds', __DIR__ . '/core');

        define('PPWPPROPLUGINSADS_LOADED', 1);
    }
}, $loadingPriority);

Well, it seems like Jetpack already implemented a solution for this using an autolaoder for composer:

https://github.com/Automattic/jetpack-autoloader