Function Reference/register widget

 /*Description
================*/

Registers a widget.

 /*Usage
================*/

<?php register_widget( $widget_class ) ?>

 /*Parameters
================*/

$widget_class
    (object) The name of a class[div] that extends WP_Widget

/*Example
=========*/

class MyNewWidget extends WP_Widget {

    function MyNewWidget() {
        // Instantiate the parent object
        parent::__construct( false, 'My New Widget Title' );
    }

    function widget( $args, $instance ) {
        // Widget output
    }

    function update( $new_instance, $old_instance ) {
        // Save widget options
    }

    function form( $instance ) {
        // Output admin widget options form
    }
}

function myplugin_register_widgets() {
    register_widget( 'MyNewWidget' );
}

add_action( 'widgets_init', 'myplugin_register_widgets' );