PHP自动加载功能不起作用 - wamp

I have strange problem with autoload function.

my structure is like this

Project
 |
 +-- test.php
 |    
 +-- class
 |  |  
 |  +-- class.news.php

I have this code:

function __autoload($class_name) {

if(file_exists('class/class.'.strtolower($class_name).'.php')){

require_once('class/class.'.strtolower($class_name).'.php'); 

} else {

 throw new Exception("Unable to load $class_name.");

}
   }

try {

$a = new News();

 } catch (Exception $e) {

 echo $e->getMessage(), "
";

 }

i got

Fatal error: Class 'News' not found

file class.news.php

class News{
    function insert($request){
        return "ok";
        }
     }

im running this on wamp server on windows 10

Use document root to avoid issues with relative paths:

$prefix = $_SERVER['DOCUMENT_ROOT'] . '/class/class.';
$filename = $prefix . strtolower($class_name) . '.php';
if(file_exists($prefix)){
    require_once($prefix); 
}