drupal template.php - theming important points

When using a template.php file in PHPTemplate themes, there are a couple of
things you might want to watch out for.
First, you can only override a theme function once. While this seems simple, there is
one circumstance in which this may be surprising.
While you can declare a template.php file in a sub-theme even if there is a
template.php in the parent, you cannot override functions declared in the parent.
If the parent's template.php declares phptemplate_breadcrumb(), then the
sub-theme's template.php cannot declare phptemplate_breadcrumb(). Doing so
will result in a PHP errors for redeclaring a function.
Second, we have seen that theme hooks (theme_<hookname>()) can be overridden
by PHPTemplate templates and also by functions in the template.php file. But what
happens if you declare both?
The phptemplate_<hookname>() function overrides the theme function that would
otherwise load the template. Therefore, if phptemplate_block() is defined in
template.php and there is a template named block.tpl.php, the phptemplate_
block() function will be called to render all blocks, and the block.tpl.php file will
never be used.
If you need to manipulate some content before it is passed to a template, don't do
this by defining phptemplate_<hookname>(). Instead, use one of the preprocessor
functions, such as phptemplate_preprocess_block(), phptemplate_preprocess_
node(), or phptemplate_preprocess_page().
At this point, we've created a new theme. We've added custom CSS, images,
PHPTemplate files, and even some custom theme hooks... what else does it take to
complete a theme?
One more thing.