Renders a system default template, which is essentially a PHP template.
$template_file: The filename of the template to render.
$variables: A keyed array of variables that will appear in the output.
The output generated by the template.
function theme_render_template($template_file, $variables) {
// Extract the variables to a local namespace
extract($variables, EXTR_SKIP);
// Start output buffering
ob_start();
// Include the template file
include DRUPAL_ROOT . '/' . $template_file;
// End buffering and return its contents
return ob_get_clean();
}