SystemLoader - A very simplle PHP class autoloader. Does not work with underscored class path conventions, but could easilly be modified to do so.

SystemLoader.php

<?php
/**
 * SystemLoader
 *
 * Autoloader for project libs and dependencies.
 *
 * @author Mark LaDoux <mark.ladoux@gmail.com>
 */
class SystemLoader
{
  /**
   * array of file paths to search for libraries.
   *
   * @access protected
   * @var    array
   */
  protected $paths = [];

  /**
   * addRoute
   *
   * @access public
   * @param  string $path base filepath to search for libraries
   * @return void
   */
  public function addRoute(string $path)
  {
    // ensure consistency in file path separator conventions.
    str_replace('\\', '/', $path);

    // ensure a trailing '/'.
    if (substr($path, -1) != '/') {
      $path = $path . '/';
    }

    // Add path to searchable array.
    $this->paths[] = $path;
  }

  /**
   * Autoload a class.
   *
   * @access public
   * @param  string $class_name Name of class to load
   * @return void
   */
  public function autoload(string $class_name)
  {
    // Iterate through all the searchable paths
    foreach ($this->paths as $path) {

      // create file_path based on the class name, don't forget to flip
      // the slashes in the namespace!
      $file_path = str_replace('\\', '/', $path . $class_name . '.php');

      // check if the class name is loaded, if not, and the file is readable,
      // load it!
      if (! class_exists($class_name, FALSE) && is_readable($file_path)) {
        include_once $file_path;

        // break out of the loop, we're done searching now!
        break;
      }
    }
  }

  /**
   * Register the autoloader
   *
   * @access public
   * @return void
   */
  public function register()
  {
    spl_autoload_register([$this, 'autoload']);
  }
}

$sysload = new SystemLoader;
$sysload->addRoute('/absolute/path/to/root/of/libraries/');
$sysload->register();