搜索框从主题层移到了区块

In previous versions, the search_box was displayed by the theme using $search_box.

Drupal 7 removes this. The search form is simply part of the block system. Theme developers will want to remove all references to $search_box in the theme, and may need to change CSS to handle the search box in the block.

Site maintainers upgrading sites from Drupal 6 to Drupal 7 will want to add the search form block to their site.