create a custom rule action in drupal7

<?php
  /**
   * Implements hook_rules_action_info().
   */
  function mysite_rules_action_info() {
    return array(
      'mysite_action_foo' => array(
        'label' => t('Klaatu Barata Necktie'),
        'group' => t('Silly Rules Examples'),
      ),
    );
  }

  /**
   * Rule action foo.
   */
  function mysite_action_foo() {
    drupal_set_message("I'm a foo for you!");
  }
  ?>