In WordPress there are many in-built functions to get all categories. These are, wp_list_categories(), get_categories(), wp_dropdown_categories() and wp_terms_checklist(). These functions are varied based on the output format of the category result they return.
These WordPress functions accept a list of optional parameters to filter categories. These parameter lists can be an array or a query string. In this tutorial, we are going to see a short note about these functions and the usage procedure.
wp_list_catergories()
wp_list_categories() creates and returns a formatted HTML code to display category lists. This function allows us to work on the formatted results by using custom walker class. This class extends Walker_Category to parse the category results.
The way of using this function is,
<?php $args = array( 'style' => 'list', 'hide_empty' => 1, ); wp_list_categories($args); ?> <?php wp_list_categories(style=list&hide_empty=1); ?>
get_categories()
This WordPress function returns categories in an object array. From this array, we can retrieve categories to create our own format. And the code is,
<?php $args = array( 'style' => 'list', 'hide_empty' => 1, ); get_categories($args); ?> <?php get_categories(style=list&hide_empty=1); ?>
wp_dropdown_categories()
This function returns WordPress categories as a dropdown list. And the way to use this function is,
<?php $args = array( 'style' => 'list', 'hide_empty' => 1, ); wp_dropdown_categories( $args ); ?>
wp_terms_checklist()
Similarly, this function returns category checkbox. wp_terms_checklist() function accepts 6 optional parameters. The code is,
<?php wp_terms_checklist($postid,$decendent_and_self,$selected_categories,$popular_categories,$walker,$checked_ontop); ?>
and the parameters are,
- $postid – To check specified post categories.
- $decendent_and_self – To return specified category checkbox with its dependent Category checkboxes.
- $selected_categories – To check specified array of categories.
- $popular_categories – To override popular categories.
- $walker – To work with the resultant HTML.
- $checked_ontop – To move checked boxes to the top of the category tree.