Recently I’ve changed my wordpress installation to run on https instead of http. When I reconfigured Piwik to run on https ( Intention: I want the tracking code to be loaded via https too in order to avoid broken content warnings …) I ran into a couple of warnings which occupy my Piwik interface ever since.
After changing the URL of the Website which should be tracked from http to https I always have warnings of the type
WARNING: /home/.sites/4/site2156/web/analytics/core/Url.php(252): Warning - preg_match(): Unknown modifier 'a' - Piwik 2.13.1 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
on every Piwik site.
Do you have any idea what might have caused the problem and how I could get rid of those warning messages?
Best regards, Alex