Adding Widget form fields dynamically

I am trying to add form field to a WordPress widget dynamically. So if the user want to add another date to an event they can click a button to get more fields.

The question is: How do save newly created input fields to my database?
Do i need to write a custom update function? Any tips?

This is how the widget looks:

This is my php code for the widget (so far):

    class Spillelister extends WP_Widget {

    public function Spillelister() {

        $widget_options = array (
            'classname' => 'spillelister-widget',
            'description' => 'Widget for å illustrere spillelister.');

        parent::WP_Widget('spillelister_widget', 'Spilleplan', $widget_options);
    }

    // The actual widget user interface
    public function widget($args, $instance) {

        extract( $args, EXTR_SKIP);
        $title = ( $instance['title'] ) ? $instance['title'] : 'Spilleplan';
        $body = ( $instance['body'] ) ? $instance['body'] : 'Ingen flere forestillinger';

        ?>

            <?php echo $before_widget; ?>
            <?php echo $before_title . $title . $after_title; ?>
            <p><?php echo $body; ?></p>

        <?php
    }

    public function update() {

    }

    public function form() {
    ?>
        <div class="date_stamp">
        <p>
            <label>Dato</label> <input type="text" class="datepicker">
            <br>
            <label>Tid</label> <input type="text">
            <span class="remove">Remove</span>
        </p>
        </div>
        <p>
            <span class="add">Add fields</span>
        </p>

    <?php 
    }


}

function spillelister_init() {
    register_widget('Spillelister');    
}
add_action('widgets_init', 'Spillelister_init');

Any tips, hints or answers are appreciated. 🙂

Interesting Question!
I’ve never seen repeatable fields used in Widgets. Giving a full would require too much work/time, so I’ll give you links to the resources I know, and hopefully you’ll make this work and share the solution with us 😉

All this examples deal with Meta Boxes, you’ll need to copy the jQuery scripts and adapt the post_meta to the Widgets case.

• Create more Meta Boxes as needed – WPSE Q&A

• Repeatable Custom Fields in a Metabox – Gist

  /**
   * Repeatable Custom Fields in a Metabox
   * Author: Helen Hou-Sandi
   *
   * From a bespoke system, so currently not modular - will fix soon
   * Note that this particular metadata is saved as one multidimensional array (serialized)
   */
  

• Repeatable Custom Fields in a Metabox – Another Gist example, no description given. This one is quite interesting as it has the code to sort the fields.