The php works fine until the tab with the respective brick is selected
and the filter is applied. Then the php is commented out even inside the
sourcerer tags.
Screenshots
the issue is solved. It must be a joomla bug. I changed text filtering for all user types, obviously forcing joomla to update
the filtering settings. Now it works, only super user has "No Filter", as it was before.
Without sourcerer, however, php code is filtered nevertheless - joomla bug...