I would like to add a custom CSS class to the <body> tag. I am using Drupal 7/Corolla.

How can I do it programmatically from my custom module?

5 Answers 5


The preprocess functions can be implemented from modules, and themes.

The preprocess function that you need is hook_preprocess_html() and the variable to set is $variables['classes_array'], which is an array containing all the classes set for the <body> element. The content of the html.tpl.php file that is used by default by Drupal (if the theme doesn't use a different template file) is the following one:

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="<?php print $language->language; ?>" version="XHTML+RDFa 1.0" dir="<?php print $language->dir; ?>"<?php print $rdf_namespaces; ?>>

<head profile="<?php print $grddl_profile; ?>">
  <?php print $head; ?>
  <title><?php print $head_title; ?></title>
  <?php print $styles; ?>
  <?php print $scripts; ?>
<body class="<?php print $classes; ?>" <?php print $attributes;?>>
  <div id="skip-link">
    <a href="#main-content" class="element-invisible element-focusable"><?php print t('Skip to main content'); ?></a>
  <?php print $page_top; ?>
  <?php print $page; ?>
  <?php print $page_bottom; ?>

In your module you just implement the preprocess function as follows:

function mymodule_preprocess_html(&$variables) {
  $variables['classes_array'][] = "new-class";

template_process() then uses $variables['classes_array'] to populate $variables['classes'] with the following code:

$variables['classes'] = implode(' ', $variables['classes_array']);


Using a preprocess function in a module is preferable if your site uses more than one theme, or if the theme set for your site is not the one you created. In this case, you are able to set your custom CSS classes, and not lose them when updating the theme, or simply changing the default theme used by your site. If your site uses just a theme, and that theme is a custom theme you created, then you can implement the preprocess function in your custom theme. As you maintain the theme, the CSS classes are not lost when updating your theme.

  • Yes, I typically tack on the module name via preprocess_html in every module so theme JS can feature detect if desired.
    – mpdonadio
    Dec 4, 2011 at 2:09

add to MODULENAME.module and clear cache

function MODULENAME_preprocess_html(&$vars) {
  $vars['classes_array'][] = 'custom-class';

Whilst you can do this through hook_preprocess_html, quite often you'll be in a completely different part of your codebase when you come to need this. If that's the case then I'd suggest that you use ctools_class_add instead:

ctools_class_add(array('class1', 'class2', 'class3'));

You can call that from anywhere as long as hook_preprocess_html hasn't yet run and the classes will be added.


Assuming you are using the pathauto module to automatically create semantic paths for your content pages based on the menu path you can use the page's path to create the classes you are looking for:

function THEMENAME_preprocess_html(&$vars) {
  $path = drupal_get_path_alias();
  $aliases = explode('/', $path);

  foreach($aliases as $alias) {
    $vars['classes_array'][] = drupal_clean_css_identifier($alias);

You can do this via template_preprocess_html(). You can put this in your template.php, wherever your theme / base theme deems most appropriate (eg, Omega preprocess folder), or in a custom module, depending on what is most appropriate.

function mytheme_preprocess_html(&$variables) {
  $variables['classes_array'][] = "class1";
  $variables['classes_array'][] = "class2";
  $variables['classes_array'][] = "class3";

Despite the names in the API reference, the theme_preprocess and theme_process functions can be called from modules, and not just themes. All you need to do is name the hook to match your module, eg mymodule_preprocess_html().


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