Which PHP Open Source site-builder (like the Liferay portlet engine) is there to use?

Question

CMS

The customer is interested in a PHP Open Source system that has an interactive WYSIWYG website page builder, similar to the one in Liferay or Bitrix.
The admin logs into the web interface. And by drag-and-drop edits the entire content of the pages. Filling with information is carried out using templates.
Have you met similar? Thank you.

Answer 1

Grapes.js
Plus many plugins for WordPress.