example plugin

class my_class {
  public $output
  public function __construct() {
    $this->output .= '<form method="post" action="' . admin_url('admin-post.php') . '">;
    $this->output .= '<input type="hidden" name="action" value="do_something"/>';
    $this->output .= '<input type="submit" value="click here"/>';
    $this->output .= '</form>';
    add_action('admin_post_do_something', array(&$this, 'do_something'));
    add_action('admin_post_nopriv_do_something', array(&$this, 'do_something'));
    add_action('admin_post_nopriv_register_do_something', array(&$this, 'do_something'));
  }
  public function do_something() {
//This doesn't get called, whenever I click the button which is displayed through display_form() from another class which is registered as a shortcode (which works), then admin-post.php in wp-admin/admin-post.php returns a blank screen.
    status_header(200);
    die('success');
  }
  public function display_form() {
    return $this->output;
  }
}