When the PHP templating engine is activated (value framework.templating.engines: ['twig', 'php'] in config.yml) when using the code sample

{{ render_hinclude(controller('...'), {'default': 'Loading...'}) }}

the following errror occures:

An exception has been thrown during the rendering of a template ("Template name "Loading..." contains invalid characters.").

Maybe a good idea is to show an info/warning when dealing with PHP templating.

See: How to Embed Asynchronous Content with hinclude.js