1. drupal
    1. 6 core.php
    2. 8
    3. 7
6 – 7 hook_theme($existing, $type, $theme, $path)

Register a module (or theme's) theme implementations.

The following parameters are all optional.


array $existing An array of existing implementations that may be used for override purposes. This is primarily useful for themes that may wish to examine existing implementations to extract data (such as arguments) so that it may properly register its own, higher priority implementations.

$type Whether a theme, module, etc. is being processed. This is primarily useful so that themes tell if they are the actual theme being called or a parent theme. May be one of:

  • 'module': A module is being checked for theme implementations.
  • 'base_theme_engine': A theme engine is being checked for a theme that is a parent of the actual theme being used.
  • 'theme_engine': A theme engine is being checked for the actual theme being used.
  • 'base_theme': A base theme is being checked for theme implementations.
  • 'theme': The actual theme in use is being checked.

$theme The actual name of theme, module, etc. that is being being processed.

$path The directory path of the theme or module, so that it doesn't need to be looked up.

Return value

array An associative array of theme hook information. The keys on the outer array are the internal names of the hooks, and the values are arrays containing information about the hook. Each array may contain the following elements:

  • variables: (required if "render element" not present) An array of variables that this theme hook uses. This value allows the theme layer to properly utilize templates. Each array key represents the name of the variable and the value will be used as the default value if it is not given when theme() is called. Template implementations receive these arguments as variables in the template file. Function implementations are passed this array data in the $variables parameter.
  • render element: (required if "variables" not present) A string that is the name of the sole renderable element to pass to the theme function. The string represents the name of the "variable" that will hold the renderable array inside any optional preprocess or process functions. Cannot be used with the "variables" item; only one or the other, not both, can be present in a hook's info array.
  • file: The file the implementation resides in. This file will be included prior to the theme being rendered, to make sure that the function or preprocess function (as needed) is actually loaded; this makes it possible to split theme functions out into separate files quite easily.
  • path: Override the path of the file to be used. Ordinarily the module or theme path will be used, but if the file will not be in the default path, include it here. This path should be relative to the Drupal root directory.
  • template: If specified, this theme implementation is a template, and this is the template file without an extension. Do not put .tpl.php on this file; that extension will be added automatically by the default rendering engine (which is PHPTemplate). If 'path', above, is specified, the template should also be in this path.
  • function: If specified, this will be the function name to invoke for this implementation. If neither 'template' nor 'function' is specified, a default function name will be assumed. For example, if a module registers the 'node' theme hook, 'theme_node' will be assigned to its function. If the chameleon theme registers the node hook, it will be assigned 'chameleon_node' as its function.
  • pattern: A regular expression pattern to be used to allow this theme implementation to have a dynamic name. The convention is to use __ to differentiate the dynamic portion of the theme. For example, to allow forums to be themed individually, the pattern might be: 'forum__'. Then, when the forum is themed, call:

    theme(array('forum__' . $tid, 'forum'), $forum)
  • preprocess functions: A list of functions used to preprocess this data. Ordinarily this won't be used; it's automatically filled in. By default, for a module this will be filled in as template_preprocess_HOOK. For a theme this will be filled in as phptemplate_preprocess and phptemplate_preprocess_HOOK as well as themename_preprocess and themename_preprocess_HOOK.
  • override preprocess functions: Set to TRUE when a theme does NOT want the standard preprocess functions to run. This can be used to give a theme FULL control over how variables are set. For example, if a theme wants total control over how certain variables in the page.tpl.php are set, this can be set to true. Please keep in mind that when this is used by a theme, that theme becomes responsible for making sure necessary variables are set.
  • type: (automatically derived) Where the theme hook is defined: 'module', 'theme_engine', or 'theme'.
  • theme path: (automatically derived) The directory path of the theme or module, so that it doesn't need to be looked up.

Related topics


modules/system/system.api.php, line 2061

function hook_theme($existing, $type, $theme, $path) {
  return array(
    'forum_display' => array(
      'variables' => array('forums' => NULL, 'topics' => NULL, 'parents' => NULL, 'tid' => NULL, 'sortby' => NULL, 'forum_per_page' => NULL),
    'forum_list' => array(
      'variables' => array('forums' => NULL, 'parents' => NULL, 'tid' => NULL),
    'forum_topic_list' => array(
      'variables' => array('tid' => NULL, 'topics' => NULL, 'sortby' => NULL, 'forum_per_page' => NULL),
    'forum_icon' => array(
      'variables' => array('new_posts' => NULL, 'num_posts' => 0, 'comment_mode' => 0, 'sticky' => 0),
    'status_report' => array(
      'render element' => 'requirements', 
      'file' => 'system.admin.inc',
    'system_date_time_settings' => array(
      'render element' => 'form', 
      'file' => 'system.admin.inc',