A feed could not be found at https://itunes.apple.com/cn/rss/topgrossingipadapplications/limit=45/xml. A feed with an invalid mime type may fall victim to this error, or SimplePie was unable to auto-discover it.. Use force_feed() if you are certain this URL is a real feed. [https://itunes.apple.com/cn/rss/topgrossingipadapplications/limit=45/xml]