Это расширение PECL
не поставляется вместе с PHP.
This extension is available for Win32 only. It provides functions
to administrate Microsoft Internet Information Server (IIS).
The extension includes function to create web sites and virtual
directories as well as configuring security and script mapping.
These functions have been added in PHP 4.
In order to use these functions you must enable the
php_iisfunc.dll DLL inside of php.ini.
Вы можете скачать DLL этого
расширения PECL со страницы
PHP Downloads или
http://snaps.php.net/.