The 'nodeapi-style' that is mentioned in the blog refers to hooks that bundle a bunch of subroutines in a single hook implementation. This is what hook_menu and hook_theme do, among others. Storing it in the database as a registry improves performance. They are not invoked often, but build a persistent list of values that can be used over and over again. This is what Larry calls registry-style hooks. Some hooks are not meant to affect the output directly, but they add to or alter a registry that is being stored in the database. Most hooks are meant to influence that (usually html) output one way or the other (call them 'normal hooks' if you like), like hook_init for example.

Hooks can be invoked anywhere between the initial http request and returning the output.

Basically, all hooks are technically similar, but there is a difference in what they to and when they do it. As far as I know, there are no official types of hooks defined. Reading Larry's blog post, I don't think he meant to say that there are only two kinds of hooks (registry-style and nodeapi-style). If someone knows any examples, I can add it here.ĭisclaimer: This is not official but how I see it. If so, that might be a sign that they should be redesigned. I assume there are also some hooks that can't be correctly put in any of these groups or are a mix of those groups. There are plans to remove these and replace with something else (oop based) or rename them to something else than hooks. hook_field_load()) but also hook_block_view().

Typical examples include node type callbacks (hook_submit, hook_view, hook_form. This are 'Hooks' which are only called for a single module, which owns something. They are often referred to as 'Callbacks'. There is also a forth group but those are actually not really hooks and they are one of the main reasons for the typical confusion about hooks. hook_menu_alter() or hook_entity_info_alter()) and also some action hooks (e.g. Hooks that can be used to change something provided by other modules, exist for almost any info hooks (e.g. I just invented that name, but these are hooks which are called when something specific happenend like hook_init(), hook_node_save(), hook_user_save(), hook_node_view() and so on.Īlter hooks. These hooks can be called any time and the returned information is often cached (static cache or persistent cache) or stored to specific tables (e.g. Many of these have a _info suffix but don't necessarly need to.

Hooks that provide information about something, typical examples are hook_entity_info(), hook_field_info(), hook_hook_info() but also hook_permission(), hook_menu(), hook_theme(), etc. All are just functions that are called because of naming conventions. I would group them in three, four groups, but there is no technical/internal difference between them.

5 types of hooks for writing examples