gistfile1.txt

/**
 * 
 * @param unknown_type $form
 * @param unknown_type $form_state
 * @return multitype:string NULL
 */
function multifiles_example_form($form, &$form_state) {
  $form['#tree'] = TRUE;
  $form['names_fieldset'] = array(
    '#type' => 'fieldset',
    '#title' => t('Multiple managed_file upload'),
    
    '#prefix' => '<div id="names-fieldset-wrapper">',
    '#suffix' => '</div>',
    );

  if (empty($form_state['num_names'])) {
    $form_state['num_names'] = 1;
  }
  for ($i = 0; $i < $form_state['num_names']; $i++) {
    $form['names_fieldset']['name'][$i] = array(
      '#title' => t('Image '.$filecount),
      '#type' => 'managed_file',
      '#upload_location' => 'public://multifiles_example_images/',
      '#default_value' =>$value,
      '#upload_validators' => array(
        'file_validate_extensions' => array('gif png jpg jpeg'),
        'file_validate_size' => array(1000000),
        ),
      );
  }
  $form['names_fieldset']['add_name'] = array(
    '#type' => 'submit',
    '#value' => t('Add one more'),
    '#submit' => array('multifiles_example_add_more_add_one'),
    '#ajax' => array(
      'callback' => 'multifiles_example_add_more_callback',
      'wrapper' => 'names-fieldset-wrapper',
      ),
    );
  if ($form_state['num_names'] > 1) {
    $form['names_fieldset']['remove_name'] = array(
      '#type' => 'submit',
      '#value' => t('Remove one'),
      '#submit' => array('multifiles_example_add_more_remove_one'),
      '#ajax' => array(
        'callback' => 'multifiles_example_add_more_callback',
        'wrapper' => 'names-fieldset-wrapper',
        ),
      );
  }
  $form['submit'] = array(
    '#type' => 'submit',
    '#value' => t('Submit'),
    );

  return $form;
}

function multifiles_example_add_more_callback($form, $form_state) {
  return $form['names_fieldset'];
}

function multifiles_example_add_more_add_one($form, &$form_state) {
  $form_state['num_names']++;
  $form_state['rebuild'] = TRUE;
}
function multifiles_example_add_more_remove_one($form, &$form_state) {
  if ($form_state['num_names'] > 1) {
    $form_state['num_names']--;
  }
  $form_state['rebuild'] = TRUE;
}