命名空间php找不到类

Question

我有结构

   one.php
   src
     two.php

one.php文件

 <?php
        function autoloadSrc($class){
        $class = preg_replace('#\\\\#',DIRECTORY_SEPARATOR , $class);
        if (file_exists('src' . DIRECTORY_SEPARATOR . $class . '.php'))
                require_once('src' . DIRECTORY_SEPARATOR . $class . '.php');
       }

        spl_autoload_register('autoloadSrc');
        $a= new src\Agg();
        echo $a -> $b;
    ?>

two.php文件

<?php
    namespace src;

        class Agg{
            public $b = "hi"
        }
    ?>

但我收到错误，它在one.php文件中找不到类Agg，我做错了什么