i have been considering my these project and that i always aspired to understand how popular Content management systems like dupral, joomla work.so i am leaning towards that direction to focus on how Content management systems like this can function. i've got a good background on zend and rather less in symfony and can use one of these. Now i want resource (books) to learn how to integrate/register modules, menus, how to build frontend designer.

What books are you able to recommend? thank you for reading through this