title: cannot get checkboxes value using drupal form api
body: <p>i have form in drupal which uploads images and has got few checkboxes in it.
  Here is the form:</p>
  
  <pre><code>$form['checklist_fieldset'] = array(
      '#type' =&gt; 'fieldset',
      '#title' =&gt; t('Check List'),
      '#collapsible' =&gt; FALSE,
      '#collapsed' =&gt; FALSE,  
    );
  $form['checklist_fieldset']['heating'] = array(
     '#type' =&gt; 'checkboxes',
     '#title' =&gt; t('Heating options'),
  
     '#options' =&gt; array(
    '0' =&gt; t('Yes'),
    '1' =&gt; t('No')
    ),
     '#description' =&gt; t('Heating details.')
    );
  </code></pre>
  
  <p>and here is my submit function where i am processing image upload and grabbing the checkboxes value as well. I am getting the success message and image is getting uploaded but not getting the value of check boxes.</p>
  
  <pre><code>function property_add_view_submit($form,&amp;$form_state){
  $validators = array();
  
  
  
  if($file = file_save_upload('p_file1',$validators,file_direcotry_path)){
  $heating = array_keys($form_state['values']['heating']);
  drupal_set_message(t('Property Saved! '.$heating));
  dpm( $form_state['values']['heating']);
  }
  </code></pre>