Renders an element.
This function renders an element using drupal_render(). The top level element is shown with show() before rendering, so it will always be rendered even if hide() had been previously used on it.
$element: The element to be rendered.
The rendered element.
show()
hide()
function render(&$element) {
  if (!$element && $element !== 0) {
    return NULL;
  }
  if (is_array($element)) {
    show($element);
    return drupal_render($element);
  }
  else {
    // Safe-guard for inappropriate use of render() on flat variables: return
    // the variable as-is.
    return $element;
  }
}