Andrew Dorokhov
All categories of the site
$categories = get_categories();
Every element is an object with the following properties:
if ( $categories ) {
foreach ( $categories as $cat ) {
// $cat->term_id
// $cat->name (Category 1)
// $cat->slug (category-1)
// $cat->term_group (0)
// $cat->term_taxonomy_id (4)
// $cat->taxonomy (category)
// $cat->description (Description text)
// $cat->parent (0)
// $cat->count (14)
// $cat->object_id (2743)
// $cat->cat_ID (4)
// $cat->category_count (14)
// $cat->category_description (Description text)
// $cat->cat_name (Category 1)
// $cat->category_nicename (category-1)
// $cat->category_parent (0)
}
}
Categories of the current post
Inside the loop, get_the_category() returns the categories of the post being rendered:
$categories = [];
foreach ( get_the_category() as $category ) {
$categories[] = $category->name;
}
$categories_list = implode( ', ', $categories );
To get the same list already formatted as links, use get_the_category_list():
get_the_category_list( $separator, $parents, $post_id );
// Example:
$categories_list = get_the_category_list( ', ' );
Categories are just one taxonomy — see taxonomies and terms for registering your own and for querying posts by term.