class Test
{
 public function index(Demo $demo,Apple $apple){
  $demo->show();
  $apple->fun();
 }
}

$demo = new Demo();
$apple = new Apple();
$obj = new Test();
$obj->index($demo,$apple);

$obj = new dependencyInjection();
$obj->fun("Test","index");

<?php
/**
 * Created by PhpStorm.
 * User: zhezhao
 * Date: 2016/8/10
 * Time: 19:18
 */
class dependencyInjection
{
 function fun($className,$action){
  $reflectionMethod = new ReflectionMethod($className,$action);
  $parammeters = $reflectionMethod->getParameters();
  $params = array();
  foreach ($parammeters as $item) {
   preg_match('/> ([^ ]*)/',$item,$arr);
   $class = trim($arr[1]);
   $params[] = new $class();
  }
  $instance = new $className();
  $res = call_user_func_array([$instance,$action],$params);
  return $res;
 }
}