if(function_exists('register_sidebar')) {

    register_sidebar(
    array(
         'name' => __('Main Sidebar'),
         'id' => 'main-sidebar',
         'description' => __('The main sidebar area'),
         'before_widget' => '<div class="widget">',
         'after_widget' => '</div>',
         'before_title' => '<h2>',
         'after_title' => '</h2>'
   ));

}

/****************************************************/
/* Load Custom Widgets */
/***************************************************/

require_once('functions/rh_tags.php');

<?php
class RH_Tags extends WP_Widget {
    function __construct() {
        $params = array(
            'name' => 'Creative : Tag Cloud Widget',
            'description' => 'Displays info of your blog'
            );
        parent:: __construct('RH_Tags','',$params);
    }

    public function form($instance) {
        //display our form in widget page
        extract($instance);
        ?>
        <p>
            <label for="<?php echo $this->get_field_id('title') ?>">Title : </label>
            <input class="widefat" id="<?php echo $this->get_field_id('title') ?>" name="<?php echo $this->get_field_name('title') ?>"
            value="<?php if(isset($title)) echo esc_attr($title); ?>" />
        </p>
        <?php
    }

    public function widget($args,$instance) {
        //displays our widget
        extract($args);
        extract($instance);
        echo $before_widget;
           echo $before_title .$title. $after_title;
           echo '<div class="label">';
           echo "<ul>";
                echo "<li>";
                echo the_tags(' ',' ');
                echo "</li>";
                echo "</ul>";
           echo '</div>';
        echo $after_widget;
    }
}

add_action('widgets_init','rh_register_tags');
function rh_register_tags() {
    register_widget('RH_Tags');
}

function get_the_terms( $post, $taxonomy ) {
    if ( ! $post = get_post( $post ) )
        return false;

    $terms = get_object_term_cache( $post->ID, $taxonomy );
    if ( false === $terms ) {
        $terms = wp_get_object_terms( $post->ID, $taxonomy );
        wp_cache_add($post->ID, $terms, $taxonomy . '_relationships');
    }

public function( Array $args )
{
    $foo = isset( $args['foo'] )
        ? $args['foo']
        : 'my default';
    // work with `$foo`