theme
Generate the themed output.
All requests for theme hooks must go through this function. It examines the request and routes it to the appropriate theme function. The theme registry is checked to determine which implementation to use, which may be a function or a template.
If the implementation is a template, the following functions may be used to modify the $variables array. They are processed in two distinct phases; "preprocess" and "process" functions. The order listed here is the order in which they execute.
- template_preprocess(&$variables) This sets a default set of variables for all template implementations.
- template_preprocess_HOOK(&$variables) This is the first preprocessor called specific to the hook; it should be implemented by the module that registers it.
- MODULE_preprocess(&$variables) This will be called for all templates; it should only be used if there is a real need. It's purpose is similar to template_preprocess().
- MODULE_preprocess_HOOK(&$variables) This is for modules that want to alter or provide extra variables for theming hooks not registered to itself. For example, if a module named "foo" wanted to alter the $classes_array variable for the hook "node" a preprocess function of foo_preprocess_node() can be created to intercept and alter the variable.
- ENGINE_engine_preprocess(&$variables) This function should only be implemented by theme engines and exists so that it can set necessary variables for all hooks.
- ENGINE_engine_preprocess_HOOK(&$variables) This is the same as the previous function, but it is called for a single theming hook.
- THEME_preprocess(&$variables) This is for themes that want to alter or provide extra variables. For example, if a theme named "foo" wanted to alter the $classes_array variable for the hook "node" a preprocess function of foo_preprocess_node() can be created to intercept and alter the variable.
- THEME_preprocess_HOOK(&$variables) The same applies from the previous function, but it is called for a specific hook.
- template_process(&$variables) This sets a default set of variables for all template implementations.
- template_process_HOOK(&$variables) This is the first processor called specific to the hook; it should be implemented by the module that registers it.
- MODULE_process(&$variables) This will be called for all templates; it should only be used if there is a real need. It's purpose is similar to template_process().
- MODULE_process_HOOK(&$variables) This is for modules that want to alter or provide extra variables for theming hooks not registered to itself. For example, if a module named "foo" wanted to alter the $classes_array variable for the hook "node" a process function of foo_process_node() can be created to intercept and alter the variable.
- ENGINE_engine_process(&$variables) This function should only be implemented by theme engines and exists so that it can set necessary variables for all hooks.
- ENGINE_engine_process_HOOK(&$variables) This is the same as the previous function, but it is called for a single theming hook.
- ENGINE_process(&$variables) This is meant to be used by themes that utilize a theme engine. It is provided so that the processor is not locked into a specific theme. This makes it easy to share and transport code but theme authors must be careful to prevent fatal re-declaration errors when using sub-themes that have their own processor named exactly the same as its base theme. In the default theme engine (PHPTemplate), sub-themes will load their own template.php file in addition to the one used for its parent theme. This increases the risk for these errors. A good practice is to use the engine name for the base theme and the theme name for the sub-themes to minimize this possibility.
- ENGINE_process_HOOK(&$variables) The same applies from the previous function, but it is called for a specific hook.
- THEME_process(&$variables) These functions are based upon the raw theme; they should primarily be used by themes that do not use an engine or by sub-themes. It serves the same purpose as ENGINE_process().
- THEME_process_HOOK(&$variables) The same applies from the previous function, but it is called for a specific hook.
If the implementation is a function, only the hook-specific preprocess and process functions (the ones ending in _HOOK) are called from the above list. This is because theme hooks with function implementations need to be fast, and calling the non-hook-specific preprocess and process functions for them would incur a noticeable performance penalty.
There are two special variables that these preprocess and process functions can set: 'theme_hook_suggestion' and 'theme_hook_suggestions'. These will be merged together to form a list of 'suggested' alternate hooks to use, in reverse order of priority. theme_hook_suggestion will always be a higher priority than items in theme_hook_suggestions. theme() will use the highest priority implementation that exists. If none exists, theme() will use the implementation for the theme hook it was called with. These suggestions are similar to and are used for similar reasons as calling theme() with an array as the $hook parameter (see below). The difference is whether the suggestions are determined by the code that calls theme() or by a preprocess or process function.
Parameters
$hook The name of the theme hook to call. If the name contains a double-underscore ('__') and there isn't an implementation for the full name, the part before the '__' is checked. This allows a fallback to a more generic implementation. For example, if theme('links__node', ...) is called, but there is no implementation of that hook, then the 'links' implementation is used. This process is iterative, so if theme('links__contextual__node', ...) is called, theme() checks for the following implementations, and uses the first one that exists:
- links__contextual__node
- links__contextual
- links
This allows themes to create specific theme implementations for named objects and contexts of otherwise generic theme hooks. The $hook parameter may also be an array, in which case the first hook that has an implementation is used. This allows for the code that calls theme() to explicitly specify the fallback order in a situation where using the '__' convention is not desired or insufficient.
$variables An associative array of variables to merge with defaults from the theme registry, pass to preprocess and process functions for modification, and finally, pass to the function or template implementing the theme hook. Alternatively, this can be a renderable array, in which case, its properties are mapped to variables expected by the theme hook implementations.
Return value
An HTML string that generates the themed output.
Code
includes/theme.inc, line 767
<?php
function theme($hook, $variables = array()) {
static $hooks = NULL;
if (!isset($hooks)) {
drupal_theme_initialize();
$hooks = theme_get_registry();
}
// If an array of hook candidates were passed, use the first one that has an
// implementation.
if (is_array($hook)) {
foreach ($hook as $candidate) {
if (isset($hooks[$candidate])) {
break;
}
}
$hook = $candidate;
}
// If there's no implementation, check for more generic fallbacks. If there's
// still no implementation, log an error and return an empty string.
if (!isset($hooks[$hook])) {
// Iteratively strip everything after the last '__' delimiter, until an
// implementation is found.
while ($pos = strrpos($hook, '__')) {
$hook = substr($hook, 0, $pos);
if (isset($hooks[$hook])) {
break;
}
}
if (!isset($hooks[$hook])) {
watchdog('theme', 'Theme key "@key" not found.', array('@key' => $hook), WATCHDOG_WARNING);
return '';
}
}
$info = $hooks[$hook];
global $theme_path;
$temp = $theme_path;
// point path_to_theme() to the currently used theme path:
$theme_path = $info['theme path'];
// Include a file if the theme function or variable processor is held elsewhere.
if (!empty($info['includes'])) {
foreach ($info['includes'] as $include_file) {
include_once DRUPAL_ROOT . '/' . $include_file;
}
}
// If a renderable array is passed as $variables, then set $variables to
// the arguments expected by the theme function.
if (isset($variables['#theme']) || isset($variables['#theme_wrappers'])) {
$element = $variables;
$variables = array();
if (isset($info['variables'])) {
foreach (array_keys($info['variables']) as $name) {
if (isset($element["#$name"])) {
$variables[$name] = $element["#$name"];
}
}
}
else {
$variables[$info['render element']] = $element;
}
}
// Merge in argument defaults.
if (!empty($info['variables'])) {
$variables += $info['variables'];
}
elseif (!empty($info['render element'])) {
$variables += array($info['render element'] => array());
}
// Invoke the variable processors, if any. The processors may specify
// alternate suggestions for which hook's template/function to use.
if (isset($info['preprocess functions']) || isset($info['process functions'])) {
$variables['theme_hook_suggestions'] = array();
foreach (array('preprocess functions', 'process functions') as $phase) {
if (!empty($info[$phase])) {
foreach ($info[$phase] as $processor_function) {
if (function_exists($processor_function)) {
// We don't want a poorly behaved process function changing $hook.
$hook_clone = $hook;
$processor_function($variables, $hook_clone);
}
}
}
}
// If the preprocess/process functions specified hook suggestions, and the
// suggestion exists in the theme registry, use it instead of the hook that
// theme() was called with. This allows the preprocess/process step to
// route to a more specific theme hook. For example, a function may call
// theme('node', ...), but a preprocess function can add 'node__article' as
// a suggestion, enabling a theme to have an alternate template file for
// article nodes. Suggestions are checked in the following order:
// - The 'theme_hook_suggestion' variable is checked first. It overrides
// all others.
// - The 'theme_hook_suggestions' variable is checked in FILO order, so the
// last suggestion added to the array takes precedence over suggestions
// added earlier.
$suggestions = array();
if (!empty($variables['theme_hook_suggestions'])) {
$suggestions = $variables['theme_hook_suggestions'];
}
if (!empty($variables['theme_hook_suggestion'])) {
$suggestions[] = $variables['theme_hook_suggestion'];
}
foreach (array_reverse($suggestions) as $suggestion) {
if (isset($hooks[$suggestion])) {
$info = $hooks[$suggestion];
break;
}
}
}
// Generate the output using either a function or a template.
if (isset($info['function'])) {
if (function_exists($info['function'])) {
$output = $info['function']($variables);
}
}
else {
// Default render function and extension.
$render_function = 'theme_render_template';
$extension = '.tpl.php';
// The theme engine may use a different extension and a different renderer.
global $theme_engine;
if (isset($theme_engine)) {
if ($info['type'] != 'module') {
if (function_exists($theme_engine . '_render_template')) {
$render_function = $theme_engine . '_render_template';
}
$extension_function = $theme_engine . '_extension';
if (function_exists($extension_function)) {
$extension = $extension_function();
}
}
}
// In some cases, a template implementation may not have had
// template_preprocess() run (for example, if the default implementation is
// a function, but a template overrides that default implementation). In
// these cases, a template should still be able to expect to have access to
// the variables provided by template_preprocess(), so we add them here if
// they don't already exist. We don't want to run template_preprocess()
// twice (it would be inefficient and mess up zebra striping), so we use the
// 'directory' variable to determine if it has already run, which while not
// completely intuitive, is reasonably safe, and allows us to save on the
// overhead of adding some new variable to track that.
if (!isset($variables['directory'])) {
$default_template_variables = array();
template_preprocess($default_template_variables, $hook);
$variables += $default_template_variables;
}
// Render the output using the template file.
$template_file = $info['template'] . $extension;
if (isset($info['path'])) {
$template_file = $info['path'] . '/' . $template_file;
}
$output = $render_function($template_file, $variables);
}
// restore path_to_theme()
$theme_path = $temp;
return $output;
}
?>