A P P E N D I X C
Page Rendering and Altering
One of the fundamental changes in Drupal 7 is how the HTML appearing in the browser is assembled. For example, in previous Drupal versions, the content of a block was returned as an HTML string. Then, the
theme_block() function put this HTML in a template together with the subject, returned a somewhat bigger HTML string, and concatenating several of these together yielded the HTML for one region.
In Drupal 7, on the other hand, the content of the block is returned as an array from the block callback. Then it gets put inside an array and so on. The end result is a gigantic, multi-dimensional ...