Alter the default, hook-independent variables for all templates.
Allows modules to provide additional default template variables or manipulate existing. This hook is invoked from template_preprocess() after basic default template variables have been set up and before the next template preprocess function is invoked.
Note that the default template variables are statically cached within a request. When adding a template variable that depends on other context, it is your responsibility to appropriately reset the static cache in template_preprocess() when needed:
drupal_static_reset('template_preprocess');
See user_template_preprocess_default_variables_alter() for an example.
array $variables: An associative array of default template variables, as set up by _template_preprocess_default_variables(). Passed by reference.
_template_preprocess_default_variables()
Note: this list is generated by pattern matching, so it may include some functions that are not actually implementations of this hook.
function hook_template_preprocess_default_variables_alter(&$variables) {
$variables['is_admin'] = user_access('access administration pages');
}