I need to retrieve the name of all the categories that a given user has published posts for. If I can also get a URL for the archive of that cat for that user only, this would make me very happy.

How do I get a list of all categories that a given user has written blog posts for (and possibly the URL for that user's cat specific archive)?

What I've got so far:

From what I have learned, I have guessed:

  $args=array();
  $args['taxonomy']='categories';
  $args['hide_empty']=TRUE;
  $args['???']=$user_id;
  $list = get_terms( $args );

or maybe

  $cats = get_categories( 'hide_empty=0' . '???' );

One, both, or neither of these might be what I need. Can anyone help me get this across the finish line?

I need to retrieve the name of all the categories that a given user has published posts for. If I can also get a URL for the archive of that cat for that user only, this would make me very happy.

How do I get a list of all categories that a given user has written blog posts for (and possibly the URL for that user's cat specific archive)?

What I've got so far:

From what I have learned, I have guessed:

  $args=array();
  $args['taxonomy']='categories';
  $args['hide_empty']=TRUE;
  $args['???']=$user_id;
  $list = get_terms( $args );

or maybe

  $cats = get_categories( 'hide_empty=0' . '???' );

One, both, or neither of these might be what I need. Can anyone help me get this across the finish line?

• categories
• terms
• advanced-taxonomy-queries

• You're going to need SQL for this one. – Jacob Peattie Commented Jun 13, 2019 at 6:13
• Dang. Should have expected that my luck would run out sooner or later. SQL it is then. – Matthew Brown aka Lord Matt Commented Jun 13, 2019 at 6:23

2 Answers 2

As, much as I know about WordPress we have to ways to achieve this.

First: You have to retrieve all posts written by an author an then you can fetch categories assigned to those posts. Store them in an array uniquely.

$args = array('author' => $author->ID, 'posts_per_page' => -1, 'fields' => 'ids');
$authorArticles = get_posts($args);
$postList = array();
foreach($authorArticles as $key => $article){
    if(!in_array($article, $postList)){
        $postList[$key] = $article;
    }
}
$termsList = array();
$siteURL = site_url('/category/');
foreach($postList as $article){
    $terms = get_the_terms($article, 'category');
    foreach($terms as $term){
        if(!isset($termsList[$term->term_id])){
            $termsList[$term->term_id] = ['term_id' => $term->term_id, 'term_url' => $siteURL.$term->slug];
        }           
    }
}
echo '<pre>', print_r($termsList), '</pre>';

Second: As, suggested by @Jacob you have to use SQL for retrieving list of categories.

Best Regards,

You don't need SQL (but it would be more direct, also harder to maintain…).

I understand you are looking for two things:

• Get all categories of posts by one user (answered by first answer, IMHO)
• Filter categories archive by author (answered here)

One of the joys of WordPress categories is that you can pass (almost) any of the variables in WP_Query in through the URL. So, to see a list of posts by user ID 1 for category ID 3, the URL would be https://example/?cat=3&author=1. Similarly, you can simulate this in code but you'll need to use a taxonomy query as you are querying posts, not categories (I know, that sounds weird but that's how it is).

See this for a really detailed list of ways to query WordPress