WP_Widget_Pages

class WP_Widget_Pages extends WP_Widget {

	/**
	 * Sets up a new Pages widget instance.
	 *
	 * @since WP-2.8.0
	 */
	public function __construct() {
		$widget_ops = array(
			'classname' => 'widget_pages',
			'description' => __( 'A list of your site’s Pages.' ),
			'customize_selective_refresh' => true,
		);
		parent::__construct( 'pages', __( 'Pages' ), $widget_ops );
	}

	/**
	 * Outputs the content for the current Pages widget instance.
	 *
	 * @since WP-2.8.0
	 *
	 * @param array $args     Display arguments including 'before_title', 'after_title',
	 *                        'before_widget', and 'after_widget'.
	 * @param array $instance Settings for the current Pages widget instance.
	 */
	public function widget( $args, $instance ) {
		$title = ! empty( $instance['title'] ) ? $instance['title'] : __( 'Pages' );

		/**
		 * Filters the widget title.
		 *
		 * @since WP-2.6.0
		 *
		 * @param string $title    The widget title. Default 'Pages'.
		 * @param array  $instance Array of settings for the current widget.
		 * @param mixed  $id_base  The widget ID.
		 */
		$title = apply_filters( 'widget_title', $title, $instance, $this->id_base );

		$sortby = empty( $instance['sortby'] ) ? 'menu_order' : $instance['sortby'];
		$exclude = empty( $instance['exclude'] ) ? '' : $instance['exclude'];

		if ( $sortby == 'menu_order' )
			$sortby = 'menu_order, post_title';

		/**
		 * Filters the arguments for the Pages widget.
		 *
		 * @since WP-2.8.0
		 * @since WP-4.9.0 Added the `$instance` parameter.
		 *
		 * @see wp_list_pages()
		 *
		 * @param array $args     An array of arguments to retrieve the pages list.
		 * @param array $instance Array of settings for the current widget.
		 */
		$out = wp_list_pages( apply_filters( 'widget_pages_args', array(
			'title_li'    => '',
			'echo'        => 0,
			'sort_column' => $sortby,
			'exclude'     => $exclude
		), $instance ) );

		if ( ! empty( $out ) ) {
			echo $args['before_widget'];
			if ( $title ) {
				echo $args['before_title'] . $title . $args['after_title'];
			}
		?>
		<ul>
			<?php echo $out; ?>
		</ul>
		<?php
			echo $args['after_widget'];
		}
	}

	/**
	 * Handles updating settings for the current Pages widget instance.
	 *
	 * @since WP-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'] );
		if ( in_array( $new_instance['sortby'], array( 'post_title', 'menu_order', 'ID' ) ) ) {
			$instance['sortby'] = $new_instance['sortby'];
		} else {
			$instance['sortby'] = 'menu_order';
		}

		$instance['exclude'] = sanitize_text_field( $new_instance['exclude'] );

		return $instance;
	}

	/**
	 * Outputs the settings form for the Pages widget.
	 *
	 * @since WP-2.8.0
	 *
	 * @param array $instance Current settings.
	 */
	public function form( $instance ) {
		//Defaults
		$instance = wp_parse_args( (array) $instance, array( 'sortby' => 'post_title', 'title' => '', 'exclude' => '') );
		?>
		<p>
			<label for="<?php echo esc_attr( $this->get_field_id( 'title' ) ); ?>"><?php _e( 'Title:' ); ?></label>
			<input class="widefat" id="<?php echo esc_attr( $this->get_field_id('title') ); ?>" name="<?php echo esc_attr( $this->get_field_name( 'title' ) ); ?>" type="text" value="<?php echo esc_attr( $instance['title'] ); ?>" />
		</p>
		<p>
			<label for="<?php echo esc_attr( $this->get_field_id( 'sortby' ) ); ?>"><?php _e( 'Sort by:' ); ?></label>
			<select name="<?php echo esc_attr( $this->get_field_name( 'sortby' ) ); ?>" id="<?php echo esc_attr( $this->get_field_id( 'sortby' ) ); ?>" class="widefat">
				<option value="post_title"<?php selected( $instance['sortby'], 'post_title' ); ?>><?php _e('Page title'); ?></option>
				<option value="menu_order"<?php selected( $instance['sortby'], 'menu_order' ); ?>><?php _e('Page order'); ?></option>
				<option value="ID"<?php selected( $instance['sortby'], 'ID' ); ?>><?php _e( 'Page ID' ); ?></option>
			</select>
		</p>
		<p>
			<label for="<?php echo esc_attr( $this->get_field_id( 'exclude' ) ); ?>"><?php _e( 'Exclude:' ); ?></label>
			<input type="text" value="<?php echo esc_attr( $instance['exclude'] ); ?>" name="<?php echo esc_attr( $this->get_field_name( 'exclude' ) ); ?>" id="<?php echo esc_attr( $this->get_field_id( 'exclude' ) ); ?>" class="widefat" />
			<br />
			<small><?php _e( 'Page IDs, separated by commas.' ); ?></small>
		</p>
		<?php
	}

}