batch_example.module

<?php

/**
 * @file
 * Outlines how a module can use the Batch API.
 */

/**
 * @defgroup batch_example Example: Batch API
 * @ingroup examples
 * @{
 * Outlines how a module can use the Batch API.
 *
 * Batches allow heavy processing to be spread out over several page
 * requests, ensuring that the processing does not get interrupted
 * because of a PHP timeout, while allowing the user to receive feedback
 * on the progress of the ongoing operations. It also can reduce out of memory
 * situations.
 *
 * The @link batch_example.install .install file @endlink also shows how the
 * Batch API can be used to handle long-running hook_update_N() functions.
 *
 * Two harmless batches are defined:
 * - batch 1: Load the node with the lowest nid 100 times.
 * - batch 2: Load all nodes, 20 times and uses a progressive op, loading nodes
 *   by groups of 5.
 *
 * @see batch
 */

/**
 * Batch operation for batch 1: one at a time.
 *
 * This is the function that is called on each operation in batch 1.
 */
function batch_example_op_1($id, $operation_details, &$context) {

  // Simulate long process by waiting 1/50th of a second.
  usleep(20000);

  // Store some results for post-processing in the 'finished' callback.
  // The contents of 'results' will be available as $results in the
  // 'finished' function (in this example, batch_example_finished()).
  $context['results'][] = $id;

  // Optional message displayed under the progressbar.
  $context['message'] = t('Running Batch "@id" @details', [
    '@id' => $id,
    '@details' => $operation_details,
  ]);
}

/**
 * Batch operation for batch 2: five at a time.
 *
 * This is the function that is called on each operation in batch 2.
 *
 * After each group of 5 control is returned to the batch API for later
 * continuation.
 */
function batch_example_op_2($operation_details, &$context) {

  // Use the $context['sandbox'] at your convenience to store the
  // information needed to track progression between successive calls.
  if (empty($context['sandbox'])) {
    $context['sandbox'] = [];
    $context['sandbox']['progress'] = 0;
    $context['sandbox']['current_node'] = 0;

    // Save node count for the termination message.
    $context['sandbox']['max'] = 30;
  }

  // Process in groups of 5 (arbitrary value).
  // When a group of five is processed, the batch update engine determines
  // whether it should continue processing in the same request or provide
  // progress feedback to the user and wait for the next request.
  // That way even though we're already processing at the operation level
  // the operation itself is interruptible.
  $limit = 5;

  // Retrieve the next group.
  $result = range($context['sandbox']['current_node'] + 1, $context['sandbox']['current_node'] + 1 + $limit);
  foreach ($result as $row) {

    // Here we actually perform our dummy 'processing' on the current node.
    usleep(20000);

    // Store some results for post-processing in the 'finished' callback.
    // The contents of 'results' will be available as $results in the
    // 'finished' function (in this example, batch_example_finished()).
    $context['results'][] = $row . ' ' . $operation_details;

    // Update our progress information.
    $context['sandbox']['progress']++;
    $context['sandbox']['current_node'] = $row;
    $context['message'] = t('Running Batch "@id" @details', [
      '@id' => $row,
      '@details' => $operation_details,
    ]);
  }

  // Inform the batch engine that we are not finished,
  // and provide an estimation of the completion level we reached.
  if ($context['sandbox']['progress'] != $context['sandbox']['max']) {
    $context['finished'] = $context['sandbox']['progress'] >= $context['sandbox']['max'];
  }
}

/**
 * Batch 'finished' callback used by both batch 1 and batch 2.
 */
function batch_example_finished($success, $results, $operations) {
  $messenger = \Drupal::messenger();
  if ($success) {

    // Here we could do something meaningful with the results.
    // We just display the number of nodes we processed...
    $messenger
      ->addMessage(t('@count results processed.', [
      '@count' => count($results),
    ]));
    $messenger
      ->addMessage(t('The final result was "%final"', [
      '%final' => end($results),
    ]));
  }
  else {

    // An error occurred.
    // $operations contains the operations that remained unprocessed.
    $error_operation = reset($operations);
    $messenger
      ->addMessage(t('An error occurred while processing @operation with arguments : @args', [
      '@operation' => $error_operation[0],
      '@args' => print_r($error_operation[0], TRUE),
    ]));
  }
}

/**
 * @} End of "defgroup batch_example".
 */