If allow_ur_fopen is enabled, something as simple as this should work:
$data = file_get_contents('http://feedxxx.com/index.php');
The reason that the [man]include/man failed is because it should; why would you try to include() a file across an http connection? Doesn't make sense.
Now, if you're simply trying to display/load the HTML output of a website, well, that certainly makes sense, though you should never use [man]include[/man]/[man]require[/man] for that...
Also, when posting PHP code, please use the board's [PHP][/PHP] bbcode tags - they make the code much, much easier to read (as well as aiding the diagnosis of syntax errors). You should edit your post now and add these bbcode tags to help others in reading/analyzing your code.