Render 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, $variables) {
extract($variables, EXTR_SKIP);
// Extract the variables to a local namespace
ob_start();
// Start output buffering
include DRUPAL_ROOT . '/' . $template_file;
// Include the template file
return ob_get_clean();
// End buffering and return its contents
}