Question: What is "XMLReader::open() failed to open stream: no suitable wrapper"?

Answer: It sounds like your web host has disabled allow_url_fopen in the PHP configuration on your server, which means the Comet Cache Auto-Cache Engine will be unable to access the URL to your XML Sitemap (which it uses to figure out which pages it on your site it should generate a cache file for).

As a result, you may see an error like the following in your error log whenever the Auto-Cache Engine runs:

[Wed Mar 04 23:09:25 2015] [warn] [client] mod_fcgid: stderr: PHP Warning: XMLReader::open( []: failed to open stream: no suitable wrapper could be found in /home/example/www/wp-content/plugins/comet-cache-pro/includes/auto-cache.php on line 233

Please contact your web host and ask them to enable allow_url_fopen in the PHP configuration.

Note: We currently have a feature request open to allow the Auto-Cache Engine to fallback on using cURL when allow_fopen_url is disabled. See #440 for further details and to cast your vote.