Getting posts from some categories plus some individual posts
The problem here is that WP_Query requires the posts returned to be both in your lists of post IDs and in one of your categories. The SQL query generated by your code looks something like this: SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts INNER JOIN wp_term_relationships ON (wp_posts.ID = wp_term_relationships.object_id) WHERE 1=1 AND wp_posts.ID IN (8200,3581,38,1562,7613) AND … Read more