Smart Loading for libraries in WordPress

smart-load-library.php

<?php

/**
 * Increment this number for every build. 
 * You can use an environment variable if you prefer.
 *
 * @var int
 */
$buildNumber = 1;

/**
 * As higher as the build number is, smaller will be the loading priority - loading it first and creating the load flag.
 * If the load flag is found, no other instance of the library should be loaded.
 * This way we try to guarantee that only the most updated installed version is loaded.
 *
 * @var int
 */
$loadingPriority = PHP_INT_MAX - (int)$buildNumber;

/*
 * Any unique action name is valid here. Just make sure to have a unique hook name for it.
 * You will use it later to call the library loading, making sure to do it only
 * from an event like 'init' or other that guarantee all the plugins are loaded
 * and able to register its hooks.
 */
add_action('flipper_framework_load', function () {
    if (!defined('FLIPPER_FRAMEWORK_LOADED')) {
        // Load the library
        define('FLIPPER_FRAMEWORK_VERSION', '0.1.0');

        if (!class_exists('FlipperFramework\\Autoloader')) {
            require_once 'src' . DIRECTORY_SEPARATOR . 'Autoloader.php';
        }

        Autoloader::register('FlipperFramework', __DIR__ . DIRECTORY_SEPARATOR . 'src');
  
        // Set the loaded flag
        define('FLIPPER_FRAMEWORK_LOADED', 1);
    }
}, $loadingPriority);

Instead of a build number, maybe we check for the version number. But on this case, instead of using the lower priority in the action we can register all the versions and check the highest one using version_compare before we really load the library.