Extend a plugin to include a widget option

Question

I currently have a plugin (not a widget) that allows people to use shortcode to put the results on their web pages and posts. Some people have asked for a widget option, so the output can go in the sidebar (if the theme supports it).

Is this possible? I tried putting together a dummy widget (using code from the WP docs), but if I try to activate it like this:

 add_action( 'widgets_init', 'src_load_widgets' );
  function src_load_widgets() {

 register_widget('Foo_Widget');
 }

I just get this error:

Fatal error: Class 'Foo_Widget' not found in /Users/me/My Webs/wordpress/wp-includes/widgets.php on line 324

Currently, the widget script is in the same folder as my plugin script since I want to same admin screen as I do for my plugin. Not sure if this is the problem...so basically, I'm a bit lost. Thanks for any help you can provide here.

Answer 1

A widget is a PHP object that echoes string data to STDOUT when its widget() method is called. -- WordPress Widgets API

To create the widget you have to extend the WP_Widget class with your widget class. You use the class name in the register_widget function.

class Foo_Widget extends WP_Widget {
   //Class methods here
}

function my_widgets_init() {
    register_widget( 'Foo_Widget' );
}
add_action( 'widgets_init', 'my_widgets_init' );