"Warning - preg_match(): Unknown modifier 'a'" after changing website to https

Hello everyone,

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

If you close these notifications, do they re-appear again and again? if so, please create a bug report at: Issues · matomo-org/piwik · GitHub


If I close the notification they do reappear the next time I reload the page or browse to another page. It’s also worth noting that they the number of them is varying.

Best regards, Alex

Hi Alex,

Thanks for the report. I’ve fixed the bug in: Warning - preg_match(): Unknown modifier ‘a’ · Issue #8290 · matomo-org/piwik · GitHub

It is fixed in latest 2.14.0-RC4

Hi Matt,

Thank you very much.

Best regards, Alex