求助 CodeIgniter 集成七牛 CDN 的问题

买了个老外的 php 脚本，基于 CodeIgniter 框架，但是作者不提供此项支持，给了个国外 cdn 运营商的配置范例[ https://cdnsun.com/knowledgebase/integrations/codeigniter-cdn-integration ]但是我按照此配置到自己的网站，导致页面报错 error 500 所以想咨询下有没有使用 CodeIgniter 框架的大佬帮忙看下什么问题，可以请大佬喝杯咖啡:)

1,applicaiton/config/config.php

$config['cdn_enabled']  = true;
$config['cdn_domain']   = 'cdn.domain.com';
$config['cdn_protocol'] = 'https';

2,Create a file application/helpers/cdn_helper.php

<?php

function cdn($url = null)
{
    $url = (string) $url;
    if(empty($url))
    {
        throw new Exception('URL missing');
    }

    $pattern = '|^http[s]{0,1}://|i';        
    if(preg_match($pattern, $url))
    {
        throw new Exception('Invalid URL. ' .
            'Use: /image.jpeg instead of full URI: ' .
            'https://domain.com/image.jpeg.'
        );
    }
        
    $pattern = '|^/|';        
    if(!preg_match($pattern, $url))
    {
        $url = '/' . $url;
    }

    $currentInstance    =& get_instance();
    $cdn_enabled        = $currentInstance->config->item('cdn_enabled');
    $cdn_domain         = $currentInstance->config->item('cdn_domain');
    $cdn_protocol       = $currentInstance->config->item('cdn_protocol');

    if(empty($cdn_enabled))
    {
        return $url;
    }
    else
    {
        return $cdn_protocol . '://' . $cdn_domain . $url;
    }    
}   

3,Add the following to the CodeIgniter's application/config/autoload.php file.

$autoload['helper'] = array('cdn');