Answers for "wp get all the post ids of a type"

wordpress get post id

// Retrieve the ID of the current item in the WordPress Loop.
get_the_ID()

wp get all post categories

$categories = get_categories();
foreach($categories as $category) {
   echo '<div class="col-md-4"><a href="' . get_category_link($category->term_id) . '">' . $category->name . '</a></div>';
}