I know why rss fails on my site.
The PHP option allow_url_fopen would normally allow a programmer to open, include or otherwise use a remote file using a URL rather than a local file path. For security reasons, my host provider has disabled this feature.
From my host's wiki :
Many developers include files by pointing to a remote URL, even if the file is within the local system. For example:
<?php include("http://example.com/includes/example_include.php"); ?>With allow_url_fopen disabled, this method will not work. Instead, the file must be included with a local path, and there are three methods of doing this:
By using a relative path, such as ../includes/example_include.php.
By using an absolute path (also known as relative-from-root), such as /home/username/example.com/includes/example_include.php.
By using the PHP environment variable $_SERVER['DOCUMENT_ROOT'], which returns the absolute path to the web root directory. This is by far the best (and most portable) solution. The example that follows shows the environment variable in action:
<?php include($_SERVER['DOCUMENT_ROOT']."/includes/example_include.php"); ?>
Processing Differences (and passing variables to an included file)
It is worth mentioning that the alternative solutions presented here will result in a difference in the way the include() function is handled. The alternative solutions all return the PHP code from the included page; however, the now-unavailable remote URL method returns the result from the included page. One result of this behavior is that you cannot pass a querystring using the alternative solutions. You define the variables locally before performing the include:
To achieve the effect of this:
<?php include("http://example.com/includes/example_include.php?var=example"); ?>
You must instead use this:
$var = "example";
For maximum flexibility (when multiple includes are required, for example), it may be easier to create a variable:
$doc_root = $_SERVER['DOCUMENT_ROOT'];
Note: The technique works in the same way, regardless of whether you are using include() or require().