您需要手动删除application/cache文件夹中的缓存项目。
https://www.codeigniter.com/user_guide/general/caching.html

function delete_cache($uri_string=null)
{
    $CI =& get_instance();
    $path = $CI->config->item('cache_path');
    $path = rtrim($path, DIRECTORY_SEPARATOR);

    $cache_path = ($path == '') ? APPPATH.'cache/' : $path;

    $uri =  $CI->config->item('base_url').
            $CI->config->item('index_page').
            $uri_string;

    $cache_path .= md5($uri);

    return unlink($cache_path);
}

public function clear_path_cache($uri)
{
    $CI =& get_instance();
    $path = $CI->config->item('cache_path');
    //path of cache directory
    $cache_path = ($path == '') ? APPPATH.'cache/' : $path;

    $uri =  $CI->config->item('base_url').
    $CI->config->item('index_page').
    $uri;
    $cache_path .= md5($uri);

    return @unlink($cache_path);
}



/**
 * Clears all cache from the cache directory
 */
public function clear_all_cache()
{
    $CI =& get_instance();
    $path = $CI->config->item('cache_path');

    $cache_path = ($path == '') ? APPPATH.'cache/' : $path;

    $handle = opendir($cache_path);
    while (($file = readdir($handle))!== FALSE) 
    {
        //Leave the directory protection alone
        if ($file != '.htaccess' && $file != 'index.html')
        {
           @unlink($cache_path.'/'.$file);
        }
    }
    closedir($handle);       
}

它可能在session中。请尝试删除您的Cookie。