[wp-hackers] Widget Weirdness - Doesn't like the file name widgets.php

[Mike Schinkel]

On Jun 27, 2011, at 10:46 AM, John Blackbourn wrote:
>> Your include() line is trying to include the widgets.php file inside
>> wp-admin/includes. You should either use a full path in your
>> include(), or rename the file.
> Sorry, I meant your require_once() line, not include().

I've run into that same problem with an export.php file but, for the life of me, can't figure out what in PHP is causing "wp-admin/includes" to have priority over the current directory?  I'd really like to learn how this works so I'll be able to anticipate such problems in the future.  If you or anyone else knows, I'd be thankful for an explanation.

-Mike