Did you enter the URL correctly? ("http://domain.com/") Maybe the website is using CloudFlare or forbids empty User-Agent headers... Also try logging in, if the website has errors disabled it might indicate it's not vulnerable when in fact it is.
@McBochi I'm working on it. I'll update the blog post if I discover something.
@jordanIgraham Please "echo $url . '?q=node&destination=node';" and open the output URL in the browser. Maybe you're simply not entering the URL correctly, or PHP is being blocked by some other means. Turn on error_reporting and display_errors. I can't reproduce the issue.
@milankragujevic thanks - omitted "http://" in my url - now much data, but the data is the html of the site at $url. The string 'mb_strlen() expects parameter 1 to be string' is not in the $data. If it's helpful, echo $ctx outputs "Resource id #2".