Hooks
Allow modules to interact with the Drupal core.
Drupal's module system is based on the concept of "hooks". A hook is a PHP function that is named foo_bar(), where "foo" is the name of the module (whose filename is thus foo.module) and "bar" is the name of the hook. Each hook has a defined set of parameters and a specified result type.
To extend Drupal, a module need simply implement a hook. When Drupal wishes to allow intervention from modules, it determines which modules implement a hook and call that hook in all enabled modules that implement it.
The available hooks to implement are explained here in the Hooks section of the developer documentation. The string "hook" is used as a placeholder for the module name is the hook definitions. For example, if the module file is called example.module, then hook_help() as implemented by that module would be defined as example_help().
Functions
| Name | Location | Description |
|---|---|---|
| custom_url_rewrite_inbound | developer/hooks/core.php | custom_url_rewrite_inbound is not a hook, it's a function you can add to settings.php to alter incoming requests so they map to a Drupal path. This function is called before modules are loaded and the menu system is initialized and it changes... |
| custom_url_rewrite_outbound | developer/hooks/core.php | custom_url_rewrite_outbound is not a hook, it's a function you can add to settings.php to alter all links generated by Drupal. This function is called from url(). This function is called very frequently (100+ times per page) so performance... |
| hook_access | developer/hooks/node.php | Define access restrictions. |
| hook_actions_delete | developer/hooks/core.php | Execute code after an action is deleted. |
| hook_action_info | developer/hooks/core.php | Declare information about one or more Drupal actions. |
| hook_action_info_alter | developer/hooks/core.php | Alter the actions declared by another module. |
| hook_block | developer/hooks/core.php | Declare a block or set of blocks. |
| hook_boot | developer/hooks/core.php | Perform setup tasks. See also, hook_init. |
| hook_comment | developer/hooks/core.php | Act on comments. |
| hook_cron | developer/hooks/core.php | Perform periodic actions. |
| hook_db_rewrite_sql | developer/hooks/core.php | Rewrite database queries, usually for access control. |
| hook_delete | developer/hooks/node.php | Respond to node deletion. |
| hook_disable | developer/hooks/install.php | Perform necessary actions before module is disabled. |
| hook_elements | developer/hooks/core.php | Allows modules to declare their own Forms API element types and specify their default values. |
| hook_enable | developer/hooks/install.php | Perform necessary actions after module is enabled. |
| hook_exit | developer/hooks/core.php | Perform cleanup tasks. |
| hook_file_download | developer/hooks/core.php | Control access to private file downloads and specify HTTP headers. |
| hook_filter | developer/hooks/core.php | Define content filters. |
| hook_filter_tips | developer/hooks/core.php | Provide tips for using filters. |
| hook_flush_caches | developer/hooks/core.php | Add a list of cache tables to be cleared. |
| hook_footer | developer/hooks/core.php | Insert closing HTML. |
| hook_form | developer/hooks/node.php | Display a node editing form. |
| hook_forms | developer/hooks/core.php | Map form_ids to builder functions. |
| hook_form_alter | developer/hooks/core.php | Perform alterations before a form is rendered. |
| hook_form_FORM_ID_alter | developer/hooks/core.php | Provide a form-specific alteration instead of the global hook_form_alter(). |
| hook_help | developer/hooks/core.php | Provide online user help. |
| hook_hook_info | developer/hooks/core.php | Expose a list of triggers (events) that your module is allowing users to assign actions to. |
| hook_init | developer/hooks/core.php | Perform setup tasks. See also, hook_boot. |
| hook_insert | developer/hooks/node.php | Respond to node insertion. |
| hook_install | developer/hooks/install.php | Install the current version of the database schema, and any other setup tasks. |
| hook_link | developer/hooks/core.php | Define internal Drupal links. |
| hook_link_alter | developer/hooks/core.php | Perform alterations before links on a node are rendered. One popular use of this hook is to modify/remove links from other modules. If you want to add a link to the links section of a node, use hook_link instead. |
| hook_load | developer/hooks/node.php | Load node-type-specific information. |
| hook_locale | developer/hooks/core.php | Allows modules to define their own text groups that can be translated. |
| hook_mail | developer/hooks/core.php | Prepare a message based on parameters; called from drupal_mail(). |
| hook_mail_alter | developer/hooks/core.php | Alter any aspect of email sent by Drupal. You can use this hook to add a common site footer to all outgoing email, add extra header fields, and/or modify the email in any way. HTML-izing the outgoing email is one possibility. See also drupal_mail(). |
| hook_menu | developer/hooks/core.php | Define menu items and page callbacks. |
| hook_menu_alter | developer/hooks/core.php | Alter the data being saved to the {menu_router} table after hook_menu is invoked. |
| hook_menu_link_alter | developer/hooks/core.php | Alter the data being saved to the {menu_links} table by menu_link_save(). |
| hook_nodeapi | developer/hooks/core.php | Act on nodes defined by other modules. |
| hook_node_access_records | developer/hooks/core.php | Set permissions for a node to be written to the database. |
| hook_node_grants | developer/hooks/core.php | Inform the node access system what permissions the user has. |
| hook_node_info | developer/hooks/node.php | Define module-provided node types. |
| hook_node_operations | developer/hooks/core.php | Add mass node operations. |
| hook_node_type | developer/hooks/node.php | Act on node type changes. |
| hook_perm | developer/hooks/core.php | Define user permissions. |
| hook_ping | developer/hooks/core.php | Ping another server. |
| hook_prepare | developer/hooks/node.php | This is a hook used by node modules. It is called after load but before the node is shown on the add/edit form. |
| hook_profile_alter | developer/hooks/core.php | Perform alterations profile items before they are rendered. You may omit/add/re-sort/re-categorize, etc. |
| hook_requirements | developer/hooks/install.php | Check installation requirements and do status reporting. |
| hook_schema | developer/hooks/install.php | Define the current version of the database schema. |
| hook_schema_alter | developer/hooks/core.php | Perform alterations to existing database schemas. |
| hook_search | developer/hooks/core.php | Define a custom search routine. |
| hook_search_preprocess | developer/hooks/core.php | Preprocess text for the search index. |
| hook_system_info_alter | developer/hooks/core.php | Alter the information parsed from module and theme .info files |
| hook_taxonomy | developer/hooks/core.php | Act on taxonomy changes. |
| hook_term_path | developer/hooks/core.php | Allows modules to provide an alternative path for the terms it manages. |
| hook_theme | developer/hooks/core.php | Register a module (or theme's) theme implementations. |
| hook_theme_registry_alter | developer/hooks/core.php | Alter the theme registry information returned from hook_theme(). |
| hook_translated_menu_link_alter | developer/hooks/core.php | Alter a menu link after it's translated, but before it's rendered. |
| hook_translation_link_alter | developer/hooks/core.php | Perform alterations on translation links. |
| hook_uninstall | developer/hooks/install.php | Remove any tables or variables that the module sets. |
| hook_update | developer/hooks/node.php | Respond to node updating. |
| hook_update_index | developer/hooks/core.php | Update Drupal's full-text index for this module. |
| hook_update_last_removed | developer/hooks/install.php | Return a number which is no longer available as hook_update_N(). |
| hook_update_N | developer/hooks/install.php | Perform a single update. |
| hook_update_projects_alter | developer/hooks/core.php | Alter the list of projects before fetching data and comparing versions. |
| hook_update_status_alter | developer/hooks/core.php | Alter the information about available updates for projects. |
| hook_user | developer/hooks/core.php | Act on user account actions. |
| hook_user_operations | developer/hooks/core.php | Add mass user operations. |
| hook_validate | developer/hooks/node.php | Verify a node editing form. |
| hook_view | developer/hooks/node.php | Display a node. |
| hook_watchdog | developer/hooks/core.php | Log an event message |
| hook_xmlrpc | developer/hooks/core.php | Register XML-RPC callbacks. |
| module_hook | includes/module.inc | Determine whether a module implements a hook. |
| module_implements | includes/module.inc | Determine which modules are implementing a hook. |
| module_invoke | includes/module.inc | Invoke a hook in a particular module. |
| module_invoke_all | includes/module.inc | Invoke a hook in all enabled modules that implement it. |