Below are a couple snippets and descriptions as to how you can remove posts from a particular category:
I think that you should do something like this:
1. List all categories from a post and assign then to an Array
2. unset the ID from the category you wish to remove
3. wp_update_post( array(‘ID’ => $post->ID,’post_category’ => $arraywithcats));
Here’s a look at some code:
# full code to use in loop (category is in $cat variable) is: $kategorie_wpisu = wp_get_post_categories( $post->;ID ); unset ( $kategorie_wpisu[$cat] ); wp_update_post( array( 'ID' => $post->ID, 'post_category' => $kategorie_wpisu ) ); unset ( $kategorie_wpisu );
I’ve pulled the above two discussions from a WP Hackers thread. I’ve actually needed to do this via plugin under bulk and I had used the same general method to remove WordPress posts from categories. It really works pretty much the same with settings posts to categories as well when you’re using the methods above.