Batch API

<?php
/**
 * Implements hook_menu().
 */
function ji_custom_menu() {
  $items = array();
  $items['batch_processing'] = array(
    'title' => 'Batch Processing Check',
    'description' => 'Testing Batch Processing',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('ji_custom_batch_form'),
    'access arguments' => array('access content'),
    'type' => MENU_NORMAL_ITEM,
  );

  return $items;
}

/**
* An example form
*/
function ji_custom_batch_form($form, &$form_state) {
  $form  = array();

  $batch_options = array('article' => 'Update Article Content', 'page' => 'Update Basic Page Content');
  $form['batch_type'] = array(
       '#type' => 'select',
       '#title' => t('Selected'),
       '#options' => $batch_options,
   );

  $form['submit'] = array(
    '#type' => 'submit',
    '#value' => 'Submit',
  );

  return $form;
}

/**
* Form Submit Handler
*/
function ji_custom_batch_form_submit($form, $form_state) {
  $selected_batch = $form_state['values']['batch_type'];
  ji_custom_process_batch($selected_batch);
}

/**
* The $batch can include the following values. Only 'operations'
* and 'finished' are required, all others will be set to default values.
*
* @param operations
*   An array of callbacks and arguments for the callbacks.
*   There can be one callback called one time, one callback
*   called repeatedly with different arguments, different
*   callbacks with the same arguments, one callback with no
*   arguments, etc. (Use an empty array if you want to pass
*   no arguments.)
*/
function ji_custom_process_batch($selected_batch) {
  $batch = array(
    'operations' => array(
        // You can actually chain together multiple batch processes here
      array('ji_custom_batch_check', array($selected_batch)),
    )
    // A title to be displayed to the end user when the batch starts.
    , 'title' => t('Batch API Check')
    // A callback to be used when the batch finishes.
    , 'finished' => 'ji_custom_batch_check_finished'
    // An initial message to be displayed to the end user when the batch starts.
    ,'init_message' => t('Custom Batch Check is starting.')
    // A progress message for the end user. Placeholders are available.
    , 'progress_message' => t('Processed @current out of @total.')
    // The error message that will be displayed to the end user if the batch fails
    , 'error_message' => t('Example Batch has encountered an error.')

  );

  batch_set($batch);
  // If this function was called from a form submit handler, stop here,

  // Start the batch process and tell it where to send the user when it's done.
  // In this case, we’ll send the user back to the batch_processing  page.
  batch_process('batch_processing');

}

/**
* Batch 'finished' callback
*/
function ji_custom_batch_check_finished($success, $results, $operations){
  if ($success) {
    $message = format_plural(count($results), 'One node created', '@count nodes created.');
    // Here we do something meaningful with the results.
    // $message = count($results) .' processed.';
    // $message .= theme('item_list', $results);  // D6 syntax
    drupal_set_message($message);
  } else {
    // An error occurred.
    // $operations contains the operations that remained unprocessed.
    $error_operation = reset($operations);
    $message = t('An error occurred while processing %error_operation with arguments: @arguments', array('%error_operation' => $error_operation[0], '@arguments' => print_r($error_operation[1], TRUE)));
    drupal_set_message($message, 'error');
  }

}

/**
* Main Logic Part of the Batch Implementation.
* Gets node list for the type selected. Loads the node, updates the title and saves the node
*
* @param context
*   $context is an array that will contain information about the
*   status of the batch. The values in $context will retain their
*   values as the batch progresses.
*/
function ji_custom_batch_check($selected_batch, &$context){
  /*
  Set the number of nodes you want to create within a single iteration of the batch. This number
  should be pretty low as it is the reason why we're creating the batch process in the first place.
  */
  $limit = 10;

  $query = db_select('node', 'node')
    ->fields('node', array('nid','title'))
    ->condition('node.status', 1)
    ->condition('node.type',$selected_batch);

  $result = $query->execute();

  /*
  Set the variables that need to persist throughout the batch process. These need to be set inside
  the $context array because that's what persists throughout the process.
  */
  if (!isset($context['sandbox']['progress'])) {
    $context['sandbox']['progress'] = 0;
    $context['sandbox']['current_node'] = 0;
    $context['sandbox']['max'] = $result->rowCount();
  }

  drupal_set_message(t("The type: $selected_batch"), 'status', FALSE);

  $query = db_select('node', 'node')
    ->fields('node', array('nid','title'))
    ->condition('node.status', 1)
    ->condition('node.type',$selected_batch)
    ->condition('node.nid', $context['sandbox']['current_node'], '>')
    ->range(0, $limit)
    ->orderBy('node.nid','ASC');

  $result = $query->execute();

  foreach ($result as $record) {
    $node = node_load($record->nid);
    $node->title = $node->title.' #'.$context ['sandbox']['progress'];
    node_save($node);

    // Store some result for post-processing in the finished callback.
    $context['results'][] = check_plain($node->title); // Keep a running tab of all of the nodes created.
    // Update our progress information.
    $context['sandbox']['progress']++; // Used to keep track of how many nodes we've already created.
    $context['sandbox']['current_node'] = $node->nid;
    $context['message'] = "Created node " . $record->title. " ".$context ['sandbox']['progress'];

  }

  // 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'];
  }
}
?>