CI3使用缓存

/*
|--------------------------------------------------------------------------
| Cache Directory Path
|--------------------------------------------------------------------------
|
| Leave this BLANK unless you would like to set something other than the default
| application/cache/ directory.  Use a full server path with trailing slash.
|
 */
$config['cache_path'] = APPPATH . '/cache/db/';　　　　　　//末尾必须加斜杠



|保留此空白，除非您想设置默认值以外的其他内容

|application/cache/目录。使用带有尾部斜杠的完整服务器路径。