widget.php

<?php 

/**
 * Adds widget.
 */
class Sublanguage_Widget extends WP_Widget {

	/**
	 * Register widget with WordPress.
	 */
	function __construct() {
		parent::__construct(
			'sublanguage_widget', // Base ID
			__( 'Sublanguage', 'sublanguage' ), // Name
			array( 'description' => __( 'Language switch', 'sublanguage' ), ) // Args
		);
	}

	/**
	 * Front-end display of widget.
	 *
	 * @see WP_Widget::widget()
	 *
	 * @param array $args     Widget arguments.
	 * @param array $instance Saved values from database.
	 */
	public function widget( $args, $instance ) {
		
		echo $args['before_widget'];
		
		if ( ! empty( $instance['title'] ) ) {
		
			echo $args['before_title'] . apply_filters( 'widget_title', $instance['title'] ). $args['after_title'];
			
		}
		
		do_action('sublanguage_print_language_switch', 'widget');
		
		echo $args['after_widget'];
	}

	/**
	 * Back-end widget form.
	 *
	 * @see WP_Widget::form()
	 *
	 * @param array $instance Previously saved values from database.
	 */
	public function form( $instance ) {
		$title = ! empty( $instance['title'] ) ? $instance['title'] : __( 'Languages', 'sublanguage' );
		?>
		<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( $title ); ?>">
		</p>
		<?php 
	}

	/**
	 * Sanitize widget form values as they are saved.
	 *
	 * @see WP_Widget::update()
	 *
	 * @param array $new_instance Values just sent to be saved.
	 * @param array $old_instance Previously saved values from database.
	 *
	 * @return array Updated safe values to be saved.
	 */
	public function update( $new_instance, $old_instance ) {
		
		$instance = array();
		
		$instance['title'] = ( ! empty( $new_instance['title'] ) ) ? strip_tags( $new_instance['title'] ) : '';

		return $instance;
	}

}