I also changed WordPress to a new server and tried all the steps above and it did not work. In my case it also encountered these strange path error:
wp-admin/admin/admin.php in httpdocs/wp-includes/functions.php on line 1963
In the end I found out it was a module (contact form 7), which resolved the whole mistake. Turned it off and works now fine.
I have the error in wp-includes/functions.php line 1963, just like you.
can you (or someone) explain what contact form 7 means and describe the fix a little more? thanks
(so annoying. it was working fine until an hour ago)
alternatively, with what do I replpace this code?
if ( realpath($path) == $path )<br />
return true;