<?php

/**
 * @file
 * Demonstrates use of the Cron API in Drupal - hook_cron()
 */

/**
 * @defgroup cron_example Example: Cron API
 * @ingroup examples
 * @{
 * Example using Cron API. (drupal 6)
 *
 * Demonstrates use of the Cron API in Drupal - hook_cron()
 *
 * This example is part of the Examples for Developers Project
 * which you can download and experiment with here:
 * http://drupal.org/project/examples
 */

/**
 * Implements hook_menu()
 * Set up a page with a link to cron.php on it.
 */
function cron_example_menu() {

  // Cron isn't typically called through a menu option.
  // Instead it is invoked through cron.php and the call to drupal_cron_run.
  // So, this menu item will just provide a way for people to fire cron.php.
  $items['cron_example'] = array(
    'title' => 'Cron Example: Trigger cron.php',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('cron_example_form'),
    'access arguments' => array('access content'),
  );

  return $items;
}

/**
 * The form to provide a link to cron.php.
 */
function cron_example_form() {
  $form['intro'] = array(
    '#value' => t('Use this page to trigger a cron run.
                   When you click the link, cron_example.module
                   will set a status message and return to this page.'),

  );
  $form['cron_trigger'] = array(
    '#type' => 'item',
    '#value' => l(t('Trigger Cron'), 'admin/reports/status/run-cron',
                  array('query' => array('destination' => 'cron_example'))),
  );

  return $form;
}

/**
 * Implements hook_cron()
 */
function cron_example_cron() {
  // This module has not actually implemented a configuration page.
  // So, there isn't a variable in the variables table to get.
  // Therefore, in our situation, the value returned will be 1.
  // But, many modules will need to provide this functionality
  // to ensure that they don't run more frequently than desired.
  $frequency = variable_get('cron_example_frequency', 1);
  // In our case, this will set the interval to daily.
  $interval = 60 * 60 * 24 * $frequency;
  // As with above, we are not actually setting the below variable anywhere.
  // Again, many modules will need to do this.
  // So, somewhere in their code they would need to do:
  // variable_set('cron_example_last_check', time())
  // using an appropriate name for the variable.
  // In our case, since we don't have an variable to get, the value
  // returned will be 0. Therefore, the current time - 0 will always be
  // greater than the interval determined above.
  if (time() - variable_get('cron_example_last_check', 0) > $interval) {
    // This is a silly example of a cron job.
    // It just makes it obvious that the job has run without
    // making any changes to your database.
    drupal_set_message(t('cron_example_cron ran!'), 'status');
  }
}

/**
 * @} End of "defgroup cron_example".
 */