WordPress 4.0 beta - how to change the link URL in RSS feeds

Question

I am using WP 4 beta and have a site at blah.com/blog but I display the posts on my site at blah.com/articles

I want all of the URLs in my RSS feed to use my site URL. Following what was mentioned here: Change the link URL in default RSS feeds

I added this filter to the bottom of plugin.php (add_filter doesn't work in functions.php in 4 beta because it's defined in plugin.php which is loaded after functions.php, I found out)

add_filter( 'the_permalink_rss', 'wpse_96602_change_feed_item_url' );

function wpse_96602_change_feed_item_url( $url )
{
return str_replace('/blog/','/article/',$url);
}

But this hasn't worked. What do I need to do? Thanks in advance :)

Answer 1

It was because my blog is at blah.com/blog but I use the WP API to actually display blog posts on another page on my site. Setting the priority of the filter to PHP_INT_MAX fixed the problem.