List categories of a custom post

Question

I have a Custom post called 'Projects'. On certain pages I need to display only the 'Projects' that have the 'apps' category. So far so good, it displays in a good way. However, when I add tags to this project, I can’t just list the tags for that particular post. So tbm as I can not list all the categories that the post contains. In the code below it returns all categories, all, including those not linked to the post

<?php
      query_posts(
        array(
          'post_type' => 'projects',
          'category_name' => 'apps',
          'showposts' => 3,
          'orderby' => 'date'
          )
        );
?>
<?php if ( have_posts() ) while ( have_posts() ) : the_post(); ?>
<?php
       $categories = get_categories($postID);
       var_dump($categories);
?>

Answer 1

You can use the method wp_get_object_terms() to rescue both the tags as to the Categories, since both are taxonomias. In a minimalist way, it is possible to do

<?php

    if(have_posts()){
        while(have_posts()){
            the_post();

            $tags = wp_get_object_terms( $postID , 'post_tag' );

            var_dump($tags);

            $categories = wp_get_object_terms( $postID , 'category' );

            var_dump($categories);
        }
    }

For the purposes of curiosity, your use of the method get_categories() is incorrect. It returns a list of category objects (hence the error you find), and does not receive the $postID as an argument.