Creating a custom categories widget - php

Question

The code below is an attempt to take the WP_Widget_Categories class and use it as the basis for a custom categories widget based on the default categories widget.
I'm getting no output however and the widget is not showing up in the "Available Widgets" listing. What am I doing wrong?
<?php
/*
Plugin Name: My Categories Widget
Version: 1.0
*/
class MY_Widget_Categories extends WP_Widget {
function MY_Widget_Categories() {
$widget_ops = array( 'classname' => 'widget_categories', 'description' => __( "A list or dropdown of categories" ) );
$this->WP_Widget('categories', __('Categories'), $widget_ops);
}
function widget( $args, $instance ) {
extract( $args );
$title = apply_filters('widget_title', empty( $instance['title'] ) ? __( 'Categories' ) : $instance['title']);
$c = $instance['count'] ? '1' : '0';
$h = $instance['hierarchical'] ? '1' : '0';
$d = $instance['dropdown'] ? '1' : '0';
echo $before_widget;
if ( $title )
echo $before_title . $title . $after_title;
$cat_args = array('orderby' => 'name', 'show_count' => $c, 'hierarchical' => $h);
if ( $d ) {
$cat_args['show_option_none'] = __('Select Category');
wp_dropdown_categories(apply_filters('widget_categories_dropdown_args', $cat_args));
?>
<script type='text/javascript'>
/* <![CDATA[ */
var dropdown = document.getElementById("cat");
function onCatChange() {
if ( dropdown.options[dropdown.selectedIndex].value > 0 ) {
location.href = "<?php echo get_option('home'); ?>/?cat="+dropdown.options[dropdown.selectedIndex].value;
}
}
dropdown.onchange = onCatChange;
/* ]]> */
</script>
<?php
} else {
?>
<ul>
<?php
$cat_args['title_li'] = '';
wp_list_categories(apply_filters('widget_categories_args', $cat_args));
?>
</ul>
<?php
}
echo $after_widget;
}
function update( $new_instance, $old_instance ) {
$instance = $old_instance;
$instance['title'] = strip_tags($new_instance['title']);
$instance['count'] = $new_instance['count'] ? 1 : 0;
$instance['hierarchical'] = $new_instance['hierarchical'] ? 1 : 0;
$instance['dropdown'] = $new_instance['dropdown'] ? 1 : 0;
return $instance;
}
function form( $instance ) {
//Defaults
$instance = wp_parse_args( (array) $instance, array( 'title' => '') );
$title = esc_attr( $instance['title'] );
$count = isset($instance['count']) ? (bool) $instance['count'] :false;
$hierarchical = isset( $instance['hierarchical'] ) ? (bool) $instance['hierarchical'] : false;
$dropdown = isset( $instance['dropdown'] ) ? (bool) $instance['dropdown'] : false;
?>
<p><label for="<?php echo $this->get_field_id('title'); ?>"><?php _e( 'Title:' ); ?></label>
<input class="widefat" id="<?php echo $this->get_field_id('title'); ?>" name="<?php echo $this->get_field_name('title'); ?>" type="text" value="<?php echo $title; ?>" /></p>
<p><input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id('dropdown'); ?>" name="<?php echo $this->get_field_name('dropdown'); ?>"<?php checked( $dropdown ); ?> />
<label for="<?php echo $this->get_field_id('dropdown'); ?>"><?php _e( 'Show as dropdown' ); ?></label><br />
<input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id('count'); ?>" name="<?php echo $this->get_field_name('count'); ?>"<?php checked( $count ); ?> />
<label for="<?php echo $this->get_field_id('count'); ?>"><?php _e( 'Show post counts' ); ?></label><br />
<input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id('hierarchical'); ?>" name="<?php echo $this->get_field_name('hierarchical'); ?>"<?php checked( $hierarchical ); ?> />
<label for="<?php echo $this->get_field_id('hierarchical'); ?>"><?php _e( 'Show hierarchy' ); ?></label></p>
<?php
}
}
function my_categories_init()
{
register_sidebar_widget(__('My Categories Widget'), 'MY_Widget_Categories');
}
add_action("plugins_loaded", "my_categories_init");
?>

Answer 1

You'll need to use register_widget rather than register_sidebar_widget, as that function is for the old style widgets (that didn't extend WP_Widget or were just functions). You should to do this from a function hooked into the widgets_init action. See the Wordpress widgets API documentation for more info: http://codex.wordpress.org/Widgets_API
The following plugin works for me in WP 2.9.
/*
Plugin Name: My Categories Widget
Version: 0.1
*/
class My_Widget_Categories extends WP_Widget {
function My_Widget_Categories() {
$widget_ops = array( 'classname' => 'widget_categories', 'description' => __( "My list or dropdown of categories" ) );
$this->WP_Widget('my_categories', __('My Categories'), $widget_ops);
}
function widget( $args, $instance ) {
extract( $args );
$title = apply_filters('widget_title', empty( $instance['title'] ) ? __( 'Categories' ) : $instance['title']);
$c = $instance['count'] ? '1' : '0';
$h = $instance['hierarchical'] ? '1' : '0';
$d = $instance['dropdown'] ? '1' : '0';
echo $before_widget;
if ( $title )
echo $before_title . $title . $after_title;
$cat_args = array('orderby' => 'name', 'show_count' => $c, 'hierarchical' => $h);
if ( $d ) {
$cat_args['show_option_none'] = __('Select Category');
wp_dropdown_categories(apply_filters('widget_categories_dropdown_args', $cat_args));
?>
<script type='text/javascript'>
/* <![CDATA[ */
var dropdown = document.getElementById("cat");
function onCatChange() {
if ( dropdown.options[dropdown.selectedIndex].value > 0 ) {
location.href = "<?php echo get_option('home'); ?>/?cat="+dropdown.options[dropdown.selectedIndex].value;
}
}
dropdown.onchange = onCatChange;
/* ]]> */
</script>
<?php
} else {
?>
<ul>
<?php
$cat_args['title_li'] = '';
wp_list_categories(apply_filters('widget_categories_args', $cat_args));
?>
</ul>
<?php
}
echo $after_widget;
}
function update( $new_instance, $old_instance ) {
$instance = $old_instance;
$instance['title'] = strip_tags($new_instance['title']);
$instance['count'] = $new_instance['count'] ? 1 : 0;
$instance['hierarchical'] = $new_instance['hierarchical'] ? 1 : 0;
$instance['dropdown'] = $new_instance['dropdown'] ? 1 : 0;
return $instance;
}
function form( $instance ) {
//Defaults
$instance = wp_parse_args( (array) $instance, array( 'title' => '') );
$title = esc_attr( $instance['title'] );
$count = isset($instance['count']) ? (bool) $instance['count'] :false;
$hierarchical = isset( $instance['hierarchical'] ) ? (bool) $instance['hierarchical'] : false;
$dropdown = isset( $instance['dropdown'] ) ? (bool) $instance['dropdown'] : false;
?>
<p><label for="<?php echo $this->get_field_id('title'); ?>"><?php _e( 'Title:' ); ?></label>
<input class="widefat" id="<?php echo $this->get_field_id('title'); ?>" name="<?php echo $this->get_field_name('title'); ?>" type="text" value="<?php echo $title; ?>" /></p>
<p><input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id('dropdown'); ?>" name="<?php echo $this->get_field_name('dropdown'); ?>"<?php checked( $dropdown ); ?> />
<label for="<?php echo $this->get_field_id('dropdown'); ?>"><?php _e( 'Show as dropdown' ); ?></label><br />
<input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id('count'); ?>" name="<?php echo $this->get_field_name('count'); ?>"<?php checked( $count ); ?> />
<label for="<?php echo $this->get_field_id('count'); ?>"><?php _e( 'Show post counts' ); ?></label><br />
<input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id('hierarchical'); ?>" name="<?php echo $this->get_field_name('hierarchical'); ?>"<?php checked( $hierarchical ); ?> />
<label for="<?php echo $this->get_field_id('hierarchical'); ?>"><?php _e( 'Show hierarchy' ); ?></label></p>
<?php
}
}
add_action('widgets_init', create_function('', "register_widget('My_Widget_Categories');"));

Answer 2

Categories widget with taxonomy/category select dropdown.
<?php
/**
* Custom Post Type Categories widget class
*
* #since 1.0.0
* #package Custom Post Type Widgets
*/
class Custom_Post_Type_Widgets {
/**
* Sets up a new widget instance
*/
public function __construct() {
add_action( 'widgets_init', array( $this, 'init' ) );
}
/**
* Register widget
*/
public function init() {
if ( ! is_blog_installed() ) {
return;
}
register_widget( 'WP_Custom_Post_Type_Widgets_Categories' );
}
}
if ( ! defined( 'ABSPATH' ) ) {
exit;
}
$custom_post_type_widgets = new Custom_Post_Type_Widgets();
/**
* Core class WP_Custom_Post_Type_Widgets_Categories
*
* #since 1.0.0
*/
class WP_Custom_Post_Type_Widgets_Categories extends WP_Widget {
/**
* Sets up a new widget instance.
*
* #since 1.0.0
*
* #access public
*/
public function __construct() {
$widget_ops = array(
'classname' => 'widget_categories',
'description' => __( 'A list or dropdown of categories.', 'custom-post-type-widgets' ),
'customize_selective_refresh' => true,
);
parent::__construct( 'custom-post-type-categories', __( 'Categories (Custom Post Type)', 'custom-post-type-widgets' ), $widget_ops );
}
/**
* Outputs the content for the widget instance.
*
* #since 1.0.0
*
* #access public
*
* #param array $args Display arguments including 'before_title', 'after_title',
* 'before_widget', and 'after_widget'.
* #param array $instance Settings for the current widget instance.
*/
public function widget( $args, $instance ) {
$title = ! empty( $instance['title'] ) ? $instance['title'] : __( 'Categories', 'custom-post-type-widgets' );
/** This filter is documented in wp-includes/widgets/class-wp-widget-pages.php */
$title = apply_filters( 'widget_title', $title, $instance, $this->id_base );
$taxonomy = ! empty( $instance['taxonomy'] ) ? $instance['taxonomy'] : 'category';
$c = ! empty( $instance['count'] ) ? (bool) $instance['count'] : false;
$h = ! empty( $instance['hierarchical'] ) ? (bool) $instance['hierarchical'] : false;
$d = ! empty( $instance['dropdown'] ) ? (bool) $instance['dropdown'] : false;
echo $args['before_widget']; // WPCS: XSS ok.
if ( $title ) {
echo $args['before_title'] . $title . $args['after_title']; // WPCS: XSS ok.
}
$cat_args = array(
'orderby' => 'name',
'taxonomy' => $taxonomy,
'show_count' => $c,
'hierarchical' => $h,
);
if ( $d ) {
$dropdown_id = "{$this->id_base}-dropdown-{$this->number}";
echo '<label class="screen-reader-text" for="' . esc_attr( $dropdown_id ) . '">' . $title . '</label>'; // WPCS: XSS ok.
$cat_args['show_option_none'] = __( 'Select Category', 'custom-post-type-widgets' );
$cat_args['name'] = 'category' === $taxonomy ? 'category_name' : $taxonomy;
$cat_args['id'] = $dropdown_id;
$cat_args['value_field'] = 'slug';
?>
<form action="<?php echo esc_url( home_url() ); ?>" method="get">
<?php
/**
* Filters the arguments for the Categories widget drop-down.
*
* Filter hook: custom_post_type_widgets/categories/widget_categories_dropdown_args
*
* #since 2.8.0
* #since 4.9.0 Added the `$instance` parameter.
*
* #see wp_dropdown_categories()
*
* #param array $cat_args An array of Categories widget drop-down arguments.
* #param array $instance Array of settings for the current widget.
* #param string $this->id Widget id.
* #param string $taxonomy Taxonomy.
*/
wp_dropdown_categories(
apply_filters(
'custom_post_type_widgets/categories/widget_categories_dropdown_args',
$cat_args,
$instance,
$this->id,
$taxonomy
)
);
?>
</form>
<script>
/* <![CDATA[ */
(function() {
var dropdown = document.getElementById( "<?php echo esc_js( $dropdown_id ); ?>" );
function onCatChange() {
if ( dropdown.options[dropdown.selectedIndex].value ) {
return dropdown.form.submit();
}
}
dropdown.onchange = onCatChange;
})();
/* ]]> */
</script>
<?php
}
else {
?>
<ul>
<?php
$cat_args['title_li'] = '';
/**
* Filters the arguments for the Categories widget.
*
* Filter hook: custom_post_type_widgets/categories/widget_categories_args
*
* #see wp_list_categories()
*
* #param array $cat_args An array of Categories widget arguments.
* #param array $instance Array of settings for the current widget.
* #param string $this->id Widget id.
* #param string $taxonomy Taxonomy.
*/
wp_list_categories(
apply_filters(
'custom_post_type_widgets/categories/widget_categories_args',
$cat_args,
$instance,
$this->id,
$taxonomy
)
);
?>
</ul>
<?php
}
echo $args['after_widget']; // WPCS: XSS ok.
}
/**
* Handles updating settings for the current Archives widget instance.
*
* #since 1.0.0
*
* #access public
*
* #param array $new_instance New settings for this instance as input by the user via form() method.
* #param array $old_instance Old settings for this instance.
*
* #return array Updated settings to save.
*/
public function update( $new_instance, $old_instance ) {
$instance = $old_instance;
$instance['title'] = sanitize_text_field( $new_instance['title'] );
$instance['taxonomy'] = stripslashes( $new_instance['taxonomy'] );
$instance['count'] = ! empty( $new_instance['count'] ) ? (bool) $new_instance['count'] : false;
$instance['hierarchical'] = ! empty( $new_instance['hierarchical'] ) ? (bool) $new_instance['hierarchical'] : false;
$instance['dropdown'] = ! empty( $new_instance['dropdown'] ) ? (bool) $new_instance['dropdown'] : false;
return $instance;
}
/**
* Outputs the settings form for the widget.
*
* #since 1.0.0
*
* #access public
*
* #param array $instance Current settings.
*/
public function form( $instance ) {
$title = isset( $instance['title'] ) ? $instance['title'] : '';
$taxonomy = isset( $instance['taxonomy'] ) ? $instance['taxonomy'] : '';
$count = isset( $instance['count'] ) ? (bool) $instance['count'] : false;
$hierarchical = isset( $instance['hierarchical'] ) ? (bool) $instance['hierarchical'] : false;
$dropdown = isset( $instance['dropdown'] ) ? (bool) $instance['dropdown'] : false;
?>
<p><label for="<?php echo $this->get_field_id( 'title' ); // WPCS: XSS ok. ?>"><?php esc_html_e( 'Title:', 'custom-post-type-widgets' ); ?></label>
<input class="widefat" id="<?php echo $this->get_field_id( 'title' ); // WPCS: XSS ok. ?>" name="<?php echo $this->get_field_name( 'title' ); // WPCS: XSS ok. ?>" type="text" value="<?php echo esc_attr( $title ); ?>" /></p>
<?php
$taxonomies = get_taxonomies( array(), 'objects' );
if ( $taxonomies ) {
printf(
'<p><label for="%1$s">%2$s</label>' .
'<select class="widefat" id="%1$s" name="%3$s">',
$this->get_field_id( 'taxonomy' ),
__( 'Taxonomy:', 'custom-post-type-widgets' ),
$this->get_field_name( 'taxonomy' )
); // WPCS: XSS ok.
foreach ( $taxonomies as $taxobjects => $value ) {
if ( ! $value->hierarchical ) {
continue;
}
if ( 'nav_menu' === $taxobjects || 'link_category' === $taxobjects || 'post_format' === $taxobjects ) {
continue;
}
printf(
'<option value="%s"%s>%s</option>',
esc_attr( $taxobjects ),
selected( $taxobjects, $taxonomy, false ),
esc_html__( $value->label, 'custom-post-type-widgets' ) . ' ' . esc_html( $taxobjects )
);
}
echo '</select></p>';
}
?>
<p><input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id( 'dropdown' ); // WPCS: XSS ok. ?>" name="<?php echo $this->get_field_name( 'dropdown' ); // WPCS: XSS ok. ?>"<?php checked( $dropdown ); ?> />
<label for="<?php echo $this->get_field_id( 'dropdown' ); // WPCS: XSS ok. ?>"><?php esc_html_e( 'Display as dropdown', 'custom-post-type-widgets' ); ?></label><br />
<input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id( 'count' ); // WPCS: XSS ok. ?>" name="<?php echo $this->get_field_name( 'count' ); // WPCS: XSS ok. ?>"<?php checked( $count ); ?> />
<label for="<?php echo $this->get_field_id( 'count' ); // WPCS: XSS ok. ?>"><?php esc_html_e( 'Show post counts', 'custom-post-type-widgets' ); ?></label><br />
<input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id( 'hierarchical' ); // WPCS: XSS ok. ?>" name="<?php echo $this->get_field_name( 'hierarchical' ); // WPCS: XSS ok. ?>"<?php checked( $hierarchical ); ?> />
<label for="<?php echo $this->get_field_id( 'hierarchical' ); // WPCS: XSS ok. ?>"><?php esc_html_e( 'Show hierarchy', 'custom-post-type-widgets' ); ?></label></p>
<?php
}
}

Answer 3

I think you can use built-in wp function using this.
<?php
$args = array(
'name' => $this->get_field_name('category'),
'show_option_none' => __( 'Select category' ),
'show_count' => 1,
'orderby' => 'name',
'echo' => 0,
'selected' => $category,
'class' => 'widefat'
);
echo wp_dropdown_categories($args);
?>