function cache_example_page_form

Main page for cache_example.

Displays a page/form which outlines how Backdrop's cache works.

Related topics

File

modules/examples/cache_example/cache_example.module, line 51

Hooks implementation for the Cache Example module.

Code

function cache_example_page_form($form, &$form_state) {
  // Log execution time.
  $start_time = microtime(TRUE);

  // Cache operations implement the cache() function.
  //
  // Try to load the files count from cache. This function will accept one
  // argument:
  // - cache bin cache bin (most often a database table) where the object is to
  //   be saved.
  //
  // The Cache::get() method accepts the cache object name (cid) as its argument
  // and returns the cached object or FALSE if object does not exist.
  //
  // The shortcut function cache_get(), as in:
  // $cache = cache_get('cache_example_files_count', 'cache');
  // may alternatively be used.
  if ($cache = cache('cache')->get('cache_example_files_count')) {
    /*
     * Get cached data. Complex data types will be unserialized automatically.
     */
    $files_count = $cache->data;
  }
  else {
    // If there was no cached data available we have to search filesystem.
    // Recursively get all files from Backdrop's folder.
    $files_count = count(file_scan_directory('.', '/.*/'));

    // Since we have recalculated, we now need to store the new data into cache.
    // Complex data types will be automatically serialized before being saved
    // into cache.
    // Here we use the default setting and create a non-expiring cache item.
    // See below for an example that creates an expiring cache item.
    // Alternative syntax: cache_set('cache_example_files_count', $files_count);
    cache('cache')->set('cache_example_files_count', $files_count);
  }

  $end_time = microtime(TRUE);
  $duration = $end_time - $start_time;

  // Format intro message.
  $intro_message = '<p>' . t('This example will search the entire Backdrop folder and display a count of the files in it.') . ' ';
  $intro_message .= t('This can take a while, since there are a lot of files to be searched.') . ' ';
  $intro_message .= t('We will search filesystem just once and save output to the cache. We will use cached data for later requests.') . '</p>';
  $intro_message .= '<p>' . t('<a href="@url">Reload this page</a> to see cache in action.', array('@url' => request_uri())) . ' ';
  $intro_message .= t('You can use the button below to remove cached data.') . '</p>';

  $form['file_search'] = array(
    '#type' => 'fieldset',
    '#title' => t('File search caching'),
  );
  $form['file_search']['introduction'] = array(
    '#markup' => $intro_message,
  );

  $color = empty($cache) ? 'red' : 'green';
  $retrieval = empty($cache) ? t('calculated by traversing the filesystem') : t('retrieved from cache');

  $form['file_search']['statistics'] = array(
    '#type' => 'item',
    '#markup' => t('%count files exist in this Backdrop installation; @retrieval in @time ms. <br/>(Source: <span style="color:@color;">@source</span>)', 
    array(
      '%count' => $files_count,
      '@retrieval' => $retrieval,
      '@time' => number_format($duration * 1000, 2),
      '@color' => $color,
      '@source' => empty($cache) ? t('actual file search') : t('cached'),
    )
    ),
  );
  $form['file_search']['remove_file_count'] = array(
    '#type' => 'submit',
    '#submit' => array('cache_example_form_expire_files'),
    '#value' => t('Explicitly remove cached file count'),
  );

  $form['expiration_demo'] = array(
    '#type' => 'fieldset',
    '#title' => t('Cache expiration settings'),
  );
  $form['expiration_demo']['explanation'] = array(
    '#markup' => t('A cache item can be set as CACHE_PERMANENT, meaning that it will only be removed when explicitly cleared, or it can have an expiration time (a Unix timestamp).'),
  );
  $expiring_item = cache('cache')->get('cache_example_expiring_item');
  $item_status = $expiring_item ?
    t('Cache item exists and is set to expire at %time', array('%time' => $expiring_item->data)) :
    t('Cache item does not exist');
  $form['expiration_demo']['current_status'] = array(
    '#type' => 'item',
    '#title' => t('Current status of cache item "cache_example_expiring_item"'),
    '#markup' => $item_status,
  );
  $form['expiration_demo']['expiration'] = array(
    '#type' => 'select',
    '#title' => t('Time before cache expiration'),
    '#options' => array(
      'never_remove' => t('CACHE_PERMANENT'),
      -10 => t('Immediate expiration'),
      10 => t('10 seconds from form submission'),
      60 => t('1 minute from form submission'),
      300 => t('5 minutes from form submission'),
    ),
    '#default_value' => -10,
    '#description' => t('Any cache item can be set to only expire when explicitly cleared, or to expire at a given time.'),
  );
  $form['expiration_demo']['create_cache_item'] = array(
    '#type' => 'submit',
    '#value' => t('Create a cache item with this expiration'),
    '#submit' => array('cache_example_form_create_expiring_item'),
  );

  $form['cache_clearing'] = array(
    '#type' => 'fieldset',
    '#title' => t('Expire and remove options'),
    '#description' => t("We have APIs to expire cached items and also to just remove them."),
  );
  $form['cache_clearing']['cache_clear_type'] = array(
    '#type' => 'radios',
    '#title' => t('Type of cache clearing to do'),
    '#options' => array(
      'expire' => t('Remove items from the "cache" bin that have expired'),
      'remove_all' => t('Remove all items from the "cache" bin regardless of expiration'),
      'remove_wildcard' => t('Remove all items from the "cache" bin that match the pattern "cache_example"'),
    ),
    '#default_value' => 'expire',
  );
  // Submit button to clear cached data.
  $form['cache_clearing']['clear_expired'] = array(
    '#type' => 'submit',
    '#value' => t('Clear or expire cache'),
    '#submit' => array('cache_example_form_cache_clearing'),
    '#access' => user_access('administer site configuration'),
  );
  return $form;
}