<form method="POST">
    <h3>Editing: class-wp-widget-categories.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php
/**
 * Widget API: WP_Widget_Categories class
 *
 * @package WordPress
 * @subpackage Widgets
 * @since 4.4.0
 */

/**
 * Core class used to implement a Categories widget.
 *
 * @since 2.8.0
 *
 * @see WP_Widget
 */
class WP_Widget_Categories extends WP_Widget {

	/**
	 * Sets up a new Categories widget instance.
	 *
	 * @since 2.8.0
	 */
	public function __construct() {
		$widget_ops = array(
			'classname'                   =&gt; 'widget_categories',
			'description'                 =&gt; __( 'A list or dropdown of categories.' ),
			'customize_selective_refresh' =&gt; true,
			'show_instance_in_rest'       =&gt; true,
		);
		parent::__construct( 'categories', __( 'Categories' ), $widget_ops );
	}

	/**
	 * Outputs the content for the current Categories widget instance.
	 *
	 * @since 2.8.0
	 * @since 4.2.0 Creates a unique HTML ID for the `&lt;select&gt;` element
	 *              if more than one instance is displayed on the page.
	 *
	 * @param array $args     Display arguments including 'before_title', 'after_title',
	 *                        'before_widget', and 'after_widget'.
	 * @param array $instance Settings for the current Categories widget instance.
	 */
	public function widget( $args, $instance ) {
		static $first_dropdown = true;

		$default_title = __( 'Categories' );
		$title         = ! empty( $instance['title'] ) ? $instance['title'] : $default_title;

		/** This filter is documented in wp-includes/widgets/class-wp-widget-pages.php */
		$title = apply_filters( 'widget_title', $title, $instance, $this-&gt;id_base );

		$count        = ! empty( $instance['count'] ) ? '1' : '0';
		$hierarchical = ! empty( $instance['hierarchical'] ) ? '1' : '0';
		$dropdown     = ! empty( $instance['dropdown'] ) ? '1' : '0';

		echo $args['before_widget'];

		if ( $title ) {
			echo $args['before_title'] . $title . $args['after_title'];
		}

		$cat_args = array(
			'orderby'      =&gt; 'name',
			'show_count'   =&gt; $count,
			'hierarchical' =&gt; $hierarchical,
		);

		if ( $dropdown ) {
			printf( '&lt;form action=&quot;%s&quot; method=&quot;get&quot;&gt;', esc_url( home_url() ) );
			$dropdown_id    = ( $first_dropdown ) ? 'cat' : &quot;{$this-&gt;id_base}-dropdown-{$this-&gt;number}&quot;;
			$first_dropdown = false;

			echo '&lt;label class=&quot;screen-reader-text&quot; for=&quot;' . esc_attr( $dropdown_id ) . '&quot;&gt;' . $title . '&lt;/label&gt;';

			$cat_args['show_option_none'] = __( 'Select Category' );
			$cat_args['id']               = $dropdown_id;

			/**
			 * Filters the arguments for the Categories widget drop-down.
			 *
			 * @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.
			 */
			wp_dropdown_categories( apply_filters( 'widget_categories_dropdown_args', $cat_args, $instance ) );

			echo '&lt;/form&gt;';

			ob_start();
			?&gt;

&lt;script&gt;
(function() {
	var dropdown = document.getElementById( &quot;&lt;?php echo esc_js( $dropdown_id ); ?&gt;&quot; );
	function onCatChange() {
		if ( dropdown.options[ dropdown.selectedIndex ].value &gt; 0 ) {
			dropdown.parentNode.submit();
		}
	}
	dropdown.onchange = onCatChange;
})();
&lt;/script&gt;

			&lt;?php
			wp_print_inline_script_tag( wp_remove_surrounding_empty_script_tags( ob_get_clean() ) );
		} else {
			$format = current_theme_supports( 'html5', 'navigation-widgets' ) ? 'html5' : 'xhtml';

			/** This filter is documented in wp-includes/widgets/class-wp-nav-menu-widget.php */
			$format = apply_filters( 'navigation_widgets_format', $format );

			if ( 'html5' === $format ) {
				// The title may be filtered: Strip out HTML and make sure the aria-label is never empty.
				$title      = trim( strip_tags( $title ) );
				$aria_label = $title ? $title : $default_title;
				echo '&lt;nav aria-label=&quot;' . esc_attr( $aria_label ) . '&quot;&gt;';
			}
			?&gt;

			&lt;ul&gt;
				&lt;?php
				$cat_args['title_li'] = '';

				/**
				 * Filters the arguments for the Categories widget.
				 *
				 * @since 2.8.0
				 * @since 4.9.0 Added the `$instance` parameter.
				 *
				 * @param array $cat_args An array of Categories widget options.
				 * @param array $instance Array of settings for the current widget.
				 */
				wp_list_categories( apply_filters( 'widget_categories_args', $cat_args, $instance ) );
				?&gt;
			&lt;/ul&gt;

			&lt;?php
			if ( 'html5' === $format ) {
				echo '&lt;/nav&gt;';
			}
		}

		echo $args['after_widget'];
	}

	/**
	 * Handles updating settings for the current Categories widget instance.
	 *
	 * @since 2.8.0
	 *
	 * @param array $new_instance New settings for this instance as input by the user via
	 *                            WP_Widget::form().
	 * @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['count']        = ! empty( $new_instance['count'] ) ? 1 : 0;
		$instance['hierarchical'] = ! empty( $new_instance['hierarchical'] ) ? 1 : 0;
		$instance['dropdown']     = ! empty( $new_instance['dropdown'] ) ? 1 : 0;

		return $instance;
	}

	/**
	 * Outputs the settings form for the Categories widget.
	 *
	 * @since 2.8.0
	 *
	 * @param array $instance Current settings.
	 */
	public function form( $instance ) {
		// Defaults.
		$instance     = wp_parse_args( (array) $instance, array( 'title' =&gt; '' ) );
		$count        = isset( $instance['count'] ) ? (bool) $instance['count'] : false;
		$hierarchical = isset( $instance['hierarchical'] ) ? (bool) $instance['hierarchical'] : false;
		$dropdown     = isset( $instance['dropdown'] ) ? (bool) $instance['dropdown'] : false;
		?&gt;
		&lt;p&gt;
			&lt;label for=&quot;&lt;?php echo $this-&gt;get_field_id( 'title' ); ?&gt;&quot;&gt;&lt;?php _e( 'Title:' ); ?&gt;&lt;/label&gt;
			&lt;input class=&quot;widefat&quot; id=&quot;&lt;?php echo $this-&gt;get_field_id( 'title' ); ?&gt;&quot; name=&quot;&lt;?php echo $this-&gt;get_field_name( 'title' ); ?&gt;&quot; type=&quot;text&quot; value=&quot;&lt;?php echo esc_attr( $instance['title'] ); ?&gt;&quot; /&gt;
		&lt;/p&gt;

		&lt;p&gt;
			&lt;input type=&quot;checkbox&quot; class=&quot;checkbox&quot; id=&quot;&lt;?php echo $this-&gt;get_field_id( 'dropdown' ); ?&gt;&quot; name=&quot;&lt;?php echo $this-&gt;get_field_name( 'dropdown' ); ?&gt;&quot;&lt;?php checked( $dropdown ); ?&gt; /&gt;
			&lt;label for=&quot;&lt;?php echo $this-&gt;get_field_id( 'dropdown' ); ?&gt;&quot;&gt;&lt;?php _e( 'Display as dropdown' ); ?&gt;&lt;/label&gt;
			&lt;br /&gt;

			&lt;input type=&quot;checkbox&quot; class=&quot;checkbox&quot; id=&quot;&lt;?php echo $this-&gt;get_field_id( 'count' ); ?&gt;&quot; name=&quot;&lt;?php echo $this-&gt;get_field_name( 'count' ); ?&gt;&quot;&lt;?php checked( $count ); ?&gt; /&gt;
			&lt;label for=&quot;&lt;?php echo $this-&gt;get_field_id( 'count' ); ?&gt;&quot;&gt;&lt;?php _e( 'Show post counts' ); ?&gt;&lt;/label&gt;
			&lt;br /&gt;

			&lt;input type=&quot;checkbox&quot; class=&quot;checkbox&quot; id=&quot;&lt;?php echo $this-&gt;get_field_id( 'hierarchical' ); ?&gt;&quot; name=&quot;&lt;?php echo $this-&gt;get_field_name( 'hierarchical' ); ?&gt;&quot;&lt;?php checked( $hierarchical ); ?&gt; /&gt;
			&lt;label for=&quot;&lt;?php echo $this-&gt;get_field_id( 'hierarchical' ); ?&gt;&quot;&gt;&lt;?php _e( 'Show hierarchy' ); ?&gt;&lt;/label&gt;
		&lt;/p&gt;
		&lt;?php
	}
}
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