batch_example.module

<?php


/**
 * @file
 * This is an example outlining how a module can define batches.
 *
 * Batches allow heavy processing to be spread out over several page
 * requests, thus 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.
 */

/**
 * @defgroup batch_example Example: Batch API
 * @ingroup examples
 * @{
 * Examples using batch API. (drupal 6)
 *
 * 2 'harmless' batches are defined :
 * batch 1 : Load 100 times the node with the lowest nid
 * batch 2 : Load all nodes, 20 times
 *           (uses a progressive op : load nodes by groups of 5)
 *
 * The module defines the following pages :
 * - /batch_example/example_1 :
 *   Simple form, lets you pick the batch that should be executed
 * - /batch_example/example_2 :
 *   Multistep form : perform batch 1 and batch 2 as separate submission steps.
 * - /batch_example/example_3 :
 *   No form - start a batch simply by clicking a link
 *   (not really user friendly, should probably be avoided)
 *
 * This example is part of the Examples for Developers Project which
 * you can download and experiment with here:
 * http://drupal.org/project/examples
 */

/**
 * Implementation of hook_menu().
 */
function batch_example_menu() {
    $items = array();
    $items['batch_example'] = array(
        'title' => 'Batch example',
        'page callback' => 'drupal_get_form',
        'page arguments' => array(
            'batch_example_simple_form',
        ),
        'access callback' => TRUE,
    );
    $items['batch_example/example_1'] = array(
        'title' => 'Simple form',
        'type' => MENU_DEFAULT_LOCAL_TASK,
        'weight' => 0,
    );
    $items['batch_example/example_2'] = array(
        'title' => 'Multistep form',
        'page callback' => 'drupal_get_form',
        'page arguments' => array(
            'batch_example_multistep_form',
        ),
        'access callback' => TRUE,
        'type' => MENU_LOCAL_TASK,
        'weight' => 1,
    );
    $items['batch_example/example_3'] = array(
        'title' => 'No form',
        'page callback' => 'batch_example_page',
        'access callback' => TRUE,
        'type' => MENU_LOCAL_TASK,
        'weight' => 2,
    );
    return $items;
}

/**
 * Test 1 :
 * Simple form
 */
function batch_example_simple_form() {
    $form['batch'] = array(
        '#type' => 'select',
        '#title' => 'Choose batch',
        '#options' => array(
            'batch_1' => 'batch 1 - load a node 100 times',
            'batch_2' => 'batch 2 - load all nodes, 20 times',
        ),
    );
    $form['submit'] = array(
        '#type' => 'submit',
        '#value' => 'Go',
    );
    return $form;
}

/**
 * Submit handler for the form 'batch_example_simple_form'.
 *
 * This submit handler will be called when the user clicks 'Go' in
 * the form.
 */
function batch_example_simple_form_submit($form, &$form_state) {
    // Dropdown will return 'batch_1' or 'batch_2'
    $values =& $form_state['values'];
    // Create a string with the function name 'batch_example_batch_1'
    // or 'batch_example_batch_2'
    $function = 'batch_example_' . $values['batch'];
    // Load the $batch variable with an array containing the details
    // of what to run
    $batch = $function();
    // Start the batch process running
    batch_set($batch);
    // Redirection takes place as usual.
    $form_state['redirect'] = 'batch_example/example_2';
}

/**
 * Multistep form
 */
function batch_example_multistep_form($form_state = NULL) {
    $step = isset($form_state['storage']['step']) ? $form_state['storage']['step'] : 1;
    $form['step_display'] = array(
        '#type' => 'item',
        '#value' => 'step ' . $step,
    );
    if ($step < 3) {
        $form['submit'] = array(
            '#type' => 'submit',
            '#value' => 'Go',
        );
    }
    return $form;
}
function batch_example_multistep_form_submit($form, &$form_state) {
    $step = isset($form_state['storage']['step']) ? $form_state['storage']['step'] : 1;
    switch ($step) {
        case 1:
            drupal_set_message('step 1 submitted');
            batch_set(batch_example_batch_1());
            break;
        case 2:
            drupal_set_message('step 2 submitted');
            batch_set(batch_example_batch_2());
            // this does not seem to work ?
            $form_state['redirect'] = 'batch_example/example_3';
            break;
    }
    $form_state['storage']['step'] = $step + 1;
}
function batch_example_page() {
    batch_set(batch_example_batch_1());
    // We're not inside a form submission workflow, so we have to
    // manually trigger the batch processing - this issues a
    // drupal_goto and thus ends current request.
    // We also specify here where we want to redirect after batch
    // processing.
    batch_process('batch_example/example_1');
}

/**
 * Batch 1 : Load 100 times the node with the lowest nid
 *
 * This method does not yet do the work; it simply builds an array
 * of the work which needs to be done during the batch processing.
 * The results of this function will be passed to the batch processor
 * for actual processing.
 */
function batch_example_batch_1() {
    $nid = db_result(db_query_range("SELECT nid FROM {node} ORDER BY nid ASC", 0, 1));
    $operations = array();
    for ($i = 0; $i < 100; $i++) {
        $operations[] = array(
            'batch_example_op_1',
            array(
                $nid,
            ),
        );
    }
    // Create an array which contains an array of the operations to
    // perform and a method to call when the operations are all finished
    $batch = array(
        'operations' => $operations,
        'finished' => 'batch_example_finished',
    );
    return $batch;
}

/**
 * Batch operation for batch 1 : load a node...
 */
function batch_example_op_1($nid, &$context) {
    $node = node_load($nid, NULL, TRUE);
    // Store some result for post-processing in the finished callback.
    $context['results'][] = $node->nid . ' : ' . check_plain($node->title);
    // Optional message displayed under the progressbar.
    $context['message'] = t('Loading @title', array(
        '@title' => $node->title,
    ));
}

/**
 * Batch 2 : load all nodes 5 by 5, 20 times (Multipart operation)
 *
 * This method does not yet do the work; it simply builds an array
 * of the work which needs to be done during the batch processing.
 * The results of this function will be passed to the batch
 * processor for actual processing.
 */
function batch_example_batch_2() {
    $operations = array();
    for ($i = 0; $i < 20; $i++) {
        $operations[] = array(
            'batch_example_op_2',
            array(),
        );
    }
    $batch = array(
        'operations' => $operations,
        'finished' => 'batch_example_finished',
        // We can define custom messages instead of the default ones.
'title' => t('Processing batch 2'),
        'init_message' => t('Batch 2 is starting.'),
        'progress_message' => t('Processed @current out of @total.'),
        'error_message' => t('Batch 2 has encountered an error.'),
    );
    return $batch;
}

/**
 * Batch operation for batch 2 : load all nodes, 5 by five
 * This is a multipart operation, using the
 */
function batch_example_op_2(&$context) {
    // Use the $context['sandbox'] at your convenience to store the
    // information needed to track progression between successive calls.
    if (!isset($context['sandbox']['progress'])) {
        $context['sandbox']['progress'] = 0;
        $context['sandbox']['current_node'] = 0;
        $context['sandbox']['max'] = db_result(db_query('SELECT COUNT(DISTINCT nid) FROM {node}'));
    }
    // Process nodes by 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.
    $limit = 5;
    // Retrieve the next group of nids.
    $result = db_query_range("SELECT nid FROM {node} WHERE nid > %d ORDER BY nid ASC", $context['sandbox']['current_node'], 0, $limit);
    while ($row = db_fetch_array($result)) {
        // Here we actually perform our dummy 'processing' on the current node.
        $node = node_load($row['nid'], NULL, TRUE);
        // Store some result for post-processing in the finished callback.
        $context['results'][] = $node->nid . ' : ' . check_plain($node->title);
        // Update our progress information.
        $context['sandbox']['progress']++;
        $context['sandbox']['current_node'] = $node->nid;
        $context['message'] = check_plain($node->title);
    }
    // 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']) {
        // We should always check if the current progress is equal or greater to
        // the total number of items to process. For example, if a node is added
        // while this batch process is running, the progress value will end up being
        // one greater than the max value. This will cause an infinite loop. We
        // prevent this from happening by always checking if progress is greater
        // than or equal to max.
        $context['finished'] = 1;
    }
    else {
        $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, $operations) {
    if ($success) {
        // Here we could do something meaningful with the results.
        // We just display the number of nodes we processed...
        $message = count($results) . ' processed.';
    }
    else {
        // An error occurred.
        // $operations contains the operations that remained unprocessed.
        $error_operation = reset($operations);
        $message = 'An error occurred while processing ' . $error_operation[0] . ' with arguments :' . print_r($error_operation[0], TRUE);
    }
    drupal_set_message($message);
}

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