WordPress/WordPress

<?php
/**
 * Widget API: WP_Widget_Calendar class
 *
 * @package WordPress
 * @subpackage Widgets
 * @since 4.4.0
 */

/**
 * Core class used to implement the Calendar widget.
 *
 * @since 2.8.0
 *
 * @see WP_Widget
 */
class WP_Widget_Calendar extends WP_Widget {
    /**
     * Ensure that the ID attribute only appears in the markup once
     *
     * @since 4.4.0
     * @var int
     */
    private static $instance = 0;

    /**
     * Sets up a new Calendar widget instance.
     *
     * @since 2.8.0
     */
    public function __construct() {
        $widget_ops = array(
            'classname'                   => 'widget_calendar',
            'description'                 => __( 'A calendar of your site’s posts.' ),
            'customize_selective_refresh' => true,
            'show_instance_in_rest'       => true,
        );
        parent::__construct( 'calendar', __( 'Calendar' ), $widget_ops );
    }

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

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

        echo $args['before_widget'];
        if ( $title ) {
            echo $args['before_title'] . $title . $args['after_title'];
        }
        if ( 0 === self::$instance ) {
            echo '<div id="calendar_wrap" class="calendar_wrap">';
        } else {
            echo '<div class="calendar_wrap">';
        }
        get_calendar();
        echo '</div>';
        echo $args['after_widget'];

        ++self::$instance;
    }

    /**
     * Handles updating settings for the current Calendar 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'] );

        return $instance;
    }

    /**
     * Outputs the settings form for the Calendar widget.
     *
     * @since 2.8.0
     *
     * @param array $instance Current settings.
     */
    public function form( $instance ) {
        $instance = wp_parse_args( (array) $instance, array( 'title' => '' ) );
        ?>
        <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 esc_attr( $instance['title'] ); ?>" />
        </p>
        <?php
    }
}