WordPress plugin – IIS issues

A case of strange but true tale of woe.

A few versions back I added in some functionality to my plugin, eShop, for users to view their orders. I called the file user.php. A lot of my other files have a preface of eshop_ in them. Now at the time I thought nothing of doing this, thinking the naming was suitable. Turns out it was, but caused major grief for IIS users.

Until today, when I gained access to a site using IIS. I warned the user to backup everything first in case I messed anything up and started trying to find the cause of this strange error.

The error was this:
Fatal error: Cannot redeclare add_user() (previously declared in C:\Inetpub\vhosts\site\httpdocs\blog\wordpressDEV\wp-admin\includes\user.php:23) in C:\Inetpub\vhosts\site\httpdocs\blog\wordpressDEV\wp-admin\includes\user.php on line 44

but I wasn’t included that file…

Here is the code I had:
if(is_admin())
include 'user.php';
which I assumed would include the file from the same directory. It did, unless you were on IIS. So I changed it to:
if(is_admin())
include WP_PLUGIN_DIR.'/eshop/user.php';
which I believe has finally fixed this outstanding issue.