php语法中PSR-4自动加载语法

namespace AcmeController;
 
class HomeController
{
// ...
}
 
// 自动加载器
spl_autoload_reGISter(function ($class) {
  $class = ltrim($class, "\");
  $file = "";
   
  if ($lastNsPos = strripos($class, "\")) {
    $namespace = substr($class, 0, $lastNsPos);
    $class = substr($class, $lastNsPos + 1);
    $file = str_replace("\", DIRECTORY_SEPARATOR, $namespace) . DIRECTORY_SEPARATOR;
  }
   
  $file .= str_replace("_", DIRECTORY_SEPARATOR, $class) . ".php";
   
  if (file_exists($file)) {
    require $file;
    return true;
  }
   
  return false;
});
 
// 类自动加载
$instance = new AcmeControllerHomeController();