How to hide some categories in category list under post in wordpress?

Question

In My wodpress Blog there are some categories use for the internal work. I want to hide that categories in blog homepage category list show under each post.

I print category list as print(the_category($postID));

How to hide or make filter for that category list print under each post?

Answer 1

I'm afraid that in this case you will have to go throught the categories and have some logic here. you can use a function like this one:

function filterCategories($postId,$excluded, $separator){
    $categoriesToDisplay = '';
    $count = 0;
    $allCategories = get_the_category($postId);
    foreach($allCategories as $category) {
        if ( !in_array($category->cat_ID, $excluded) ) {

           // get that category link
           $cat_link = $get_category_link($category->cat_ID);       
           $categoriesToDisplay .= $cat_link;

           // we want a separator, but not at the end...
           if($count < count($categories)){
               $categoriesToDisplay .= $separator;
           }
        }
        $count++;
    }
        return $categoriesToDisplay;
}

It will trancate the categores you want without the excluded as links seperated by what ever you want (in this case "|") You can call it within your loop:

     <?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
     <?php $id = get_the_ID(); ?>
     <?php echo filterCategories($id, array(1,2,3,4)," | "); ?>

$categories array will be the array of categories objects what you can then display as:

I haven't tested it, but it should work.

To get the excluded categories you can use a parent category called "excluded" or something like that. than they can be available for you easily:

$excluded = wp_list_categories("child_of=".$excludedCategoriId);

Hope it helps.