Matthew, I think you missing the point.
is_readable is returning false because the the supposed /D:_Work\myapp/application/modules\articles/views\helpers/HeadLink.php doesn't actually exists (HeadLink is on ZF NOT on articles module)...
The problem is not related to open_basedit then...
Looking at your report, it looks like the issue is that you're working on a system where open_basedir is enabled, and that the file as specified does not live within the basedir as configured -- leading to the false negative.
-- Best regards, Cristian Bichis www.zftutorials.com | www.zfforums.com | www.zftalk.com | www.zflinks.com