Drupal 6 batch not executing

Anyone able to offer some ideas on this? Basically the module I'm building has a form (as per function_email_solicitors_compose), and on submission we obviously route to form_emails_solicitors_compose_submit. Here I define a batch in $batch, and batch_set the aforementioned batch. The drupal documentation says I don't need to run batch_process() if it's called from within a form_submit, which this is, but I've tried with and without. All tests have shown that it gets as far as defining the batch but never goes any further than that. email_solicitors_batch_iteration never runs. Any ideas?

As an additional bit of info, batch_get then returns the following:

Array
(
    [sets] => Array
        (
            [0] => Array
                (
                    [sandbox] => Array
                        (
                        )

                    [results] => Array
                        (
                        )

                    [success] => 
                    [title] => Emailing.
                    [operations] => Array
                        (
                            [0] => Array
                                (
                                    [0] =>

email_solicitors_batch_iteration [1] => Array ( [0] => [1] => )

                                )

                        )

                    [finished] => my_finished_callback
                    [init_message] => Initializing.<br/>&nbsp;
                    [progress_message] => Remaining

@remaining of @total. [error_message] => An error has occurred. [total] => 1 )

        )

)

The code:

function email_solicitors_compose(){
    $form['email_solicitors_subject'] = array(
        '#type' => 'textfield',
        '#title' => t('Subject'),
        '#description' => t('Enter the subject of your email'),
        '#default_value' => 'Subject',
        '#size' => 30
    );
    $form['email_solicitors_message'] = array(
        '#type' => 'textarea',
        '#title' => t('Message'),
        '#description' => t('Write your message here. <strong>Please note that we will automatically add "Dear #name", which will be personalised to the 开发者_如何转开发solicitor.</strong>'),
        '#default_value' => '',
    );
    $form['email_solicitors_submit'] = array(
        '#type' => 'submit',
        '#title' => t('Submit'),
        '#description' => t('Sumbit this form.'),
        '#default_value' => 'Submit',
    );
    return $form;
}//function email_solicitors_compose


function email_solicitors_compose_submit($form_state)
{
    $batch = array(
        'title' => t('Sending emails to solicitors'),
        'operations' => array(
            array('email_solicitors_batch_iteration', array())
        ), 
        'finished' => 'email_solicitors_batch_finished', //run this when we're finished
        'init_message' => t('Preparing to send emails'), //initialisation message
        'progress_message' => t('Sent @current out of @total messages.'),
        'error_message' => t('Sorry, something went wrong when sending emails.'),
    );// create batch array
    $info=print_r($batch,TRUE);
    drupal_set_message($info);
    batch_set($batch);
    batch_process();
}//function email_solicitors_compose_submit


function email_solicitors_batch_iteration(&$context)
{
    // Initialize sandbox the first time through.
    if (!isset($context['sandbox']['progress'])) {
        $context['sandbox']['progress'] = 0;
        $context['sandbox']['current_user_id'] = 0;
        $context['sandbox']['max'] = db_result(db_query('SELECT COUNT(DISTINCT field_solicitor_email_value) FROM content_type_solicitor'));
    }
    $comment="On item ".$context['sandbox']['progress'];
    drupal_set_message ($comment);
}//function email_solicitors_batch_iteration

function email_solicitors_batch_finished (&$context)
{
    die ('woohoo we finished');
}

As an addition to the answer Clive has given, you could consider adding the "file" parameter to the batch-array. This will tell the API where the function is located.

Example:

   $batch = array(
        'title' => t('Sending emails to solicitors'),
        'operations' => array(
            array('email_solicitors_batch_iteration', array())
        ), 
        'finished' => 'email_solicitors_batch_finished', //run this when we're finished
        'init_message' => t('Preparing to send emails'), //initialisation message
        'progress_message' => t('Sent @current out of @total messages.'),
        'error_message' => t('Sorry, something went wrong when sending emails.'),
        'file' => drupal_get_path('module', '<module_name>').'/path_to_include_file.inc',
    );

It worked for me :)

Just in case anyone is still struggling with this the previous two comments are incorrect, you do not need to explicitly set the $context['finished'] variable (see the examples module, batch_example).

The reason it's not working is simply because the batch operation function is in a file not included in the default Drupal bootstrap. If you move the batch operation function out of an include file and into the module file of an enabled module it will work.

Are you having a start of sign that the batch is beginning or just nothing happens? You are missing two information in your batch operation callback: the increase of the progress and most importantly a statement to determine when the batch should over.

  // Update our progress information.
  $context['sandbox']['progress']++;
  $context['sandbox']['current_node'] = $row['nid'];
  $context['message'] = t('Calcul des votes pour %node', array('%node' => $row['title']));

  if ($context['sandbox']['progress'] != $context['sandbox']['max']) {
    $context['finished'] = $context['sandbox']['progress'] / $context['sandbox']['max'];
  }

You do not need to call batch_process(), just batch_set() in a submit callback is everything you need. See for example http://api.worldempire.ch/api/privatemsg/privatemsg_filter--privatemsg_filter.admin.inc/function/privatemsg_filter_inbox_rebuid_form_submit/7-1.

And as Artusamak said, your batch implementation is incomplete and would result in a endless loop.