psr-4

自动加载：

 <?php

 function autoload($className)
 {
     $className = ltrim($className, '\\');
     $fileName  = '';
     $namespace = '';
     if ($lastNsPos = strrpos($className, '\\')) {
         $namespace = substr($className, 0, $lastNsPos);
         $className = substr($className, $lastNsPos + 1);
         $fileName  = str_replace('\\', DIRECTORY_SEPARATOR, $namespace) . DIRECTORY_SEPARATOR;
     }
     $fileName .= str_replace('_', DIRECTORY_SEPARATOR, $className) . '.php';

     require $fileName;
 }
 spl_autoload_register('autoload');