public PlaceholderGenerator::createPlaceholder(array $element)
Turns the given element into a placeholder.
Placeholdering allows us to avoid "poor cacheability contamination": this maps the current render array to one that only has #markup and #attached, and #attached contains a placeholder with this element's prior cacheability metadata. In other words: this placeholder is perfectly cacheable, the placeholder replacement logic effectively cordons off poor cacheability.
Parameters
array $element: The render array to create a placeholder for.
Return value
array Render array with placeholder markup and the attached placeholder replacement metadata.
Overrides PlaceholderGeneratorInterface::createPlaceholder
File
- core/lib/Drupal/Core/Render/PlaceholderGenerator.php, line 70
Class
- PlaceholderGenerator
- Turns a render array into a placeholder.
Namespace
Drupal\Core\Render
Code
public function createPlaceholder(array $element) {
$placeholder_render_array = array_intersect_key($element, [
// Placeholders are replaced with markup by executing the associated
// #lazy_builder callback, which generates a render array, and which the
// Renderer will render and replace the placeholder with.
'#lazy_builder' => TRUE,
// The cacheability metadata for the placeholder. The rendered result of
// the placeholder may itself be cached, if [#cache][keys] are specified.
'#cache' => TRUE,
]);
// Generate placeholder markup. Note that the only requirement is that this
// is unique markup that isn't easily guessable. The #lazy_builder callback
// and its arguments are put in the placeholder markup solely to simplify<<<
// debugging.
$callback = $placeholder_render_array['#lazy_builder'][0];
$arguments = UrlHelper::buildQuery($placeholder_render_array['#lazy_builder'][1]);
$token = hash('crc32b', serialize($placeholder_render_array));
$placeholder_markup = '<drupal-render-placeholder callback="' . Html::escape($callback) . '" arguments="' . Html::escape($arguments) . '" token="' . Html::escape($token) . '"></drupal-render-placeholder>';
// Build the placeholder element to return.
$placeholder_element = [];
$placeholder_element['#markup'] = Markup::create($placeholder_markup);
$placeholder_element['#attached']['placeholders'][$placeholder_markup] = $placeholder_render_array;
return $placeholder_element;
}
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