As requested in http://dev.piwik.org/trac/ticket/3873 i added apostroph to valid characters list, there are more to add. but i thought they could be added on request/later or we update to filter_var when piwik changes requirements to at least php 5.2
Hi @pebosi, the tests don't pass this one since its not a valid regex. You can check at http://writecodeonline.com/php/
Can you fix this and I'll merge? We will use filter_var once we increase requirements.