Programmatically set view header

Question

I know there is a post on how to set a view header/footer value here, but how do I set a view header/footer without having to create it through views UI first?

The reason why I want to implement a view header programmatically is because (a) I want to write php code in it, by leveraging the Drupal's API, something that is not so convenient in a textarea field, like the one that the views UI provides -and any other textarea field- plus the fact that some functions may never get invoked and (b) because I want to conditionally set/unset the view header/footer.

Answer 1

After some research I managed to answer my own question by implementing the hook_views_pre_view in my custom module. The method set_item is used to set the configuration of an item (field/sort/filter/etc) on a given display. The $print variable bares the content to be rendered in the view header, it is just an example and it can be replaced by anything. Apparently now I can take advantage of the Drupal API or even set/unset any view item conditionally.

/**
 * Implementation of hook_views_pre_view.
 */
function my_module_views_pre_view(&$view, &$display_id, &$args) {

  $path = $_GET['q'];
  // Construct the print link.
  $print = l(t('Display a printer-friendly version of this page'), '/print/' . $path . '/print-friendly',  array(
    'attributes' => array(
      'class' => array('print-friendly'),
      'target' => '_blank',
      'title'=> t('Display a printer-friendly version of this page.'),
      ),
    )
  );

  if ($view->name == 'my_view_name' && $display_id == 'my_view_display') {
    // View's header declaration.
    $item = array(
      'id' => 'area',
      'table' => 'views',
      'field' => 'area',
      'relationship' => 'none',
      'group_type' => 'group',
      'ui_name' => '', 
      'label' => '',
      'empty' => 0,
      'content' => $print,
      'format' => 'filtered_html',
      'tokenize' => 0,
    );
    // Render the header.
    $view->set_item($display_id, 'header', 'area', $item);
  }
}

Answer 2

Just as a second option, you could always use a preprocess function to override the theme hook.

For starters, turn on theme_debug in your settings.php file, clear your site cache and navigate to the page that contains the view display that you'd like to alter.

Open your browser's developer tools (e.g. Chrome: Ctrl+Shift+I, or right click and choose "Inspect") and find the display's markup within the source code. You should see something similar directly above the element.

Next, inside template.php of your theme, write a preprocess function that calls the same theme hook:

function THEMENAME_preprocess_views_view(&$vars) {
    //logic
}

The $vars variable is an array that contains the view object. Use a debug tool like devel to introspect the render array. Then set the header and footer attribute by assigning it a value.

/**
 * Implements template_preprocess_views_view().
 */
function THEMENAME_preprocess_views_view(&$vars) {
    //logic
    $vars['header'] = "Something Special";
}

Source: template_preprocess_views_view