Basically, this is a programming pattern for namespacing code within a WordPress plugin. Typically, you can only have one function called init() in a program, but more than one author will try to use that name. Placing function names in a class is a way around this limitation. For example: class Towfiq_Person { static function … Read more
I would start with this question: Is the functionality related to presentation of content, or with generation/management of content, or of the site, or of the user identity? If the functionality is not related specifically to presentation of content, then it is squarely within Plugin Territory. This list is long: Modifying core WP filters (wp_head … Read more
Here you are: get_post_type() and then if ( ‘book’ == get_post_type() ) … as per Conditional Tags > A Post Type in Codex.