Hello breakling,
first I would thank you for your great work. At this moment I have a problem with your Plugin WP-PIWIK on my website. After installing and activating of your plugin, WordPress shows under the toolbar in the backend the follow message:
Warning: call_user_func_array() expects parameter 1 to be a valid callback, cannot access private method wp_piwik::onPostStatusTransition() in /homepages/27/d526774006/htdocs/pbc/wp-includes/plugin.php on line 470
This Warning Message will shown everywhere at the same position in the backend.
At first, I searched for a few websites and was landed on:
http://developer.infoymas.com/wordpress/warning-call_user_func_array-expects-parameter-1/
At the end of this post I found the follow notice:
PD: This error could be also related to plugins authors that declared a function on a previous version of their plugin and then on a newest version they delete it but forget to delete the action related.
Therefore I write this post in your forum. Hopefully you can help me.
By the way: if it is helpful I send you a private link to my website.
Thanks for your help and please excuse my bad english.
With kind regards
https://wordpress.org/plugins/wp-piwik/