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 calls 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 in 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
hook_actions_delete	modules/system/system.api.php	Executes code after an action is deleted.
hook_action_info	modules/system/system.api.php	Declares information about actions.
hook_action_info_alter	modules/system/system.api.php	Alters the actions declared by another module.
hook_admin_paths	modules/system/system.api.php	Define administrative paths.
hook_admin_paths_alter	modules/system/system.api.php	Redefine administrative paths defined by other modules.
hook_aggregator_fetch	modules/aggregator/aggregator.api.php	Implement this hook to create an alternative fetcher for aggregator module.
hook_aggregator_fetch_info	modules/aggregator/aggregator.api.php	Implement this hook to expose the title and a short description of your fetcher.
hook_aggregator_parse	modules/aggregator/aggregator.api.php	Implement this hook to create an alternative parser for aggregator module.
hook_aggregator_parse_info	modules/aggregator/aggregator.api.php	Implement this hook to expose the title and a short description of your parser.
hook_aggregator_process	modules/aggregator/aggregator.api.php	Implement this hook to create a processor for aggregator module.
hook_aggregator_process_info	modules/aggregator/aggregator.api.php	Implement this hook to expose the title and a short description of your processor.
hook_aggregator_remove	modules/aggregator/aggregator.api.php	Implement this hook to remove stored data if a feed is being deleted or a feed's items are being removed.
hook_ajax_render_alter	modules/system/system.api.php	Alter the commands that are sent to the user through the AJAX framework.
hook_archiver_info	modules/system/system.api.php	Declare archivers to the system.
hook_archiver_info_alter	modules/system/system.api.php	Alter archiver information declared by other modules.
hook_block_configure	modules/block/block.api.php	Configuration form for the block.
hook_block_info	modules/block/block.api.php	Define all blocks provided by the module.
hook_block_info_alter	modules/block/block.api.php	Act on blocks prior to rendering.
hook_block_save	modules/block/block.api.php	Save the configuration options.
hook_block_view	modules/block/block.api.php	Process the block when enabled in a region in order to view its contents.
hook_block_view_alter	modules/block/block.api.php	Perform alterations to the content of a block.
hook_block_view_MODULE_DELTA_alter	modules/block/block.api.php	Perform alterations to a specific block.
hook_boot	modules/system/system.api.php	Perform setup tasks. See also, hook_init.
hook_comment_delete	modules/comment/comment.api.php	The comment is being deleted by the moderator.
hook_comment_insert	modules/comment/comment.api.php	The comment is being inserted.
hook_comment_load	modules/comment/comment.api.php	Comments are being loaded from the database.
hook_comment_presave	modules/comment/comment.api.php	The comment passed validation and is about to be saved.
hook_comment_publish	modules/comment/comment.api.php	The comment is being published by the moderator.
hook_comment_unpublish	modules/comment/comment.api.php	The comment is being unpublished by the moderator.
hook_comment_update	modules/comment/comment.api.php	The comment is being updated.
hook_comment_view	modules/comment/comment.api.php	The comment is being viewed. This hook can be used to add additional data to the comment before theming.
hook_comment_view_alter	modules/comment/comment.api.php	The comment was built; the module may modify the structured content.
hook_countries_alter	modules/system/system.api.php	Alter the default country list.
hook_cron	modules/system/system.api.php	Perform periodic actions.
hook_cron_queue_info	modules/system/system.api.php	Declare queues holding items that need to be run periodically.
hook_cron_queue_info_alter	modules/system/system.api.php	Alter cron queue information before cron runs.
hook_css_alter	modules/system/system.api.php	Alter CSS files before they are output on the page.
hook_custom_theme	modules/system/system.api.php	Return the machine-readable name of the theme to use for the current page.
hook_dashboard_regions	modules/dashboard/dashboard.api.php	Adds regions to the dashboard.
hook_dashboard_regions_alter	modules/dashboard/dashboard.api.php	Alter dashboard regions provided by modules.
hook_date_formats	modules/system/system.api.php	Defines additional date formats.
hook_date_formats_alter	modules/system/system.api.php	Alters date types and formats declared by another module.
hook_date_format_types	modules/system/system.api.php	Defines additional date types.
hook_delete	modules/node/node.api.php	Respond to node deletion.
hook_disable	modules/system/system.api.php	Perform necessary actions before module is disabled.
hook_drupal_goto_alter	modules/system/system.api.php	Change the page the user is sent to by drupal_goto().
hook_element_info	modules/system/system.api.php	Allows modules to declare their own Forms API element types and specify their default values.
hook_element_info_alter	modules/system/system.api.php	Alter the element type information returned from modules.
hook_enable	modules/system/system.api.php	Perform necessary actions after module is enabled.
hook_entity_info	modules/system/system.api.php	Inform the base system and the Field API about one or more entity types.
hook_entity_info_alter	modules/system/system.api.php	Alter the entity info.
hook_entity_insert	modules/system/system.api.php	Act on entities when inserted.
hook_entity_load	modules/system/system.api.php	Act on entities when loaded.
hook_entity_prepare_view	modules/system/system.api.php	Act on entities as they are being prepared for view.
hook_entity_update	modules/system/system.api.php	Act on entities when updated.
hook_exit	modules/system/system.api.php	Perform cleanup tasks.
hook_file_copy	modules/system/system.api.php	Respond to a file that has been copied.
hook_file_delete	modules/system/system.api.php	Respond to a file being deleted.
hook_file_download	modules/system/system.api.php	Control access to private file downloads and specify HTTP headers.
hook_file_insert	modules/system/system.api.php	Respond to a file being added.
hook_file_load	modules/system/system.api.php	Load additional information into file objects.
hook_file_mimetype_mapping_alter	modules/system/system.api.php	Alter MIME type mappings used to determine MIME type from a file extension.
hook_file_move	modules/system/system.api.php	Respond to a file that has been moved.
hook_file_references	modules/system/system.api.php	Report the number of times a file is referenced by a module.
hook_file_update	modules/system/system.api.php	Respond to a file being updated.
hook_file_url_alter	modules/system/system.api.php	Alter the URL to a file.
hook_file_validate	modules/system/system.api.php	Check that files meet a given criteria.
hook_filter_format_delete	modules/filter/filter.api.php	Perform actions when a text format has been deleted.
hook_filter_format_insert	modules/filter/filter.api.php	Perform actions when a new text format has been created.
hook_filter_format_update	modules/filter/filter.api.php	Perform actions when a text format has been updated.
hook_filter_info	modules/filter/filter.api.php	Define content filters.
hook_filter_info_alter	modules/filter/filter.api.php	Perform alterations on filter definitions.
hook_flush_caches	modules/system/system.api.php	Add a list of cache tables to be cleared.
hook_form	modules/node/node.api.php	Display a node editing form.
hook_forms	modules/system/system.api.php	Map form_ids to form builder functions.
hook_form_alter	modules/system/system.api.php	Perform alterations before a form is rendered.
hook_form_FORM_ID_alter	modules/system/system.api.php	Provide a form-specific alteration instead of the global hook_form_alter().
hook_help	modules/help/help.api.php	Provide online user help.
hook_hook_info	modules/system/system.api.php	Defines one or more hooks that are exposed by a module.
hook_html_head_alter	modules/system/system.api.php	Alter XHTML HEAD tags before they are rendered by drupal_get_html_head().
hook_image_default_styles	modules/image/image.api.php	Provide module-based image styles for reuse throughout Drupal.
hook_image_effect_info	modules/image/image.api.php	Define information about image effects provided by a module.
hook_image_styles_alter	modules/image/image.api.php	Modify any image styles provided by other modules or the user.
hook_image_style_delete	modules/image/image.api.php	Respond to image style deletion.
hook_image_style_flush	modules/image/image.api.php	Respond to image style flushing.
hook_image_style_save	modules/image/image.api.php	Respond to image style updating.
hook_image_toolkits	modules/system/system.api.php	Define image toolkits provided by this module.
hook_init	modules/system/system.api.php	Perform setup tasks. See also, hook_boot.
hook_insert	modules/node/node.api.php	Respond to creation of a new node.
hook_install	modules/system/system.api.php	Perform setup tasks when the module is installed.
hook_install_tasks	modules/system/system.api.php	Return an array of tasks to be performed by an installation profile.
hook_install_tasks_alter	modules/system/system.api.php	Alter the full list of installation tasks.
hook_js_alter	modules/system/system.api.php	Perform necessary alterations to the JavaScript before it is presented on the page.
hook_language_fallback_candidates_alter	modules/locale/locale.api.php	Perform alterations on the language fallback candidates.
hook_language_negotiation_info	modules/locale/locale.api.php	Allow modules to define their own language providers.
hook_language_negotiation_info_alter	modules/locale/locale.api.php	Perform alterations on language providers.
hook_language_switch_links_alter	modules/locale/locale.api.php	Perform alterations on language switcher links.
hook_language_types_info	modules/locale/locale.api.php	Allow modules to define their own language types.
hook_language_types_info_alter	modules/locale/locale.api.php	Perform alterations on language types.
hook_library	modules/system/system.api.php	Registers JavaScript/CSS libraries associated with a module.
hook_library_alter	modules/system/system.api.php	Alters the JavaScript/CSS library registry.
hook_load	modules/node/node.api.php	Act on nodes being loaded from the database.
hook_locale	modules/locale/locale.api.php	Allows modules to define their own text groups that can be translated.
hook_mail	modules/system/system.api.php	Prepare a message based on parameters; called from drupal_mail().
hook_mail_alter	modules/system/system.api.php	Alter an email message created with the drupal_mail() function.
hook_menu	modules/menu/menu.api.php	Define menu items and page callbacks.
hook_menu_active_handler_alter	modules/system/system.api.php	Alters the router item for the active menu handler.
hook_menu_alter	modules/menu/menu.api.php	Alter the data being saved to the {menu_router} table after hook_menu is invoked.
hook_menu_contextual_links_alter	modules/menu/menu.api.php	Alter contextual links before they are rendered.
hook_menu_delete	modules/menu/menu.api.php	Informs modules that a custom menu was deleted.
hook_menu_insert	modules/menu/menu.api.php	Informs modules that a custom menu was created.
hook_menu_link_alter	modules/menu/menu.api.php	Alter the data being saved to the {menu_links} table by menu_link_save().
hook_menu_link_delete	modules/menu/menu.api.php	Inform modules that a menu link has been deleted.
hook_menu_link_insert	modules/menu/menu.api.php	Inform modules that a menu link has been created.
hook_menu_link_update	modules/menu/menu.api.php	Inform modules that a menu link has been updated.
hook_menu_local_tasks_alter	modules/menu/menu.api.php	Alter tabs and actions displayed on the page before they are rendered.
hook_menu_update	modules/menu/menu.api.php	Informs modules that a custom menu was updated.
hook_modules_disabled	modules/system/system.api.php	Perform necessary actions after modules are disabled.
hook_modules_enabled	modules/system/system.api.php	Perform necessary actions after modules are enabled.
hook_modules_installed	modules/system/system.api.php	Perform necessary actions after modules are installed.
hook_modules_uninstalled	modules/system/system.api.php	Perform necessary actions after modules are uninstalled.
hook_multilingual_settings_changed	modules/locale/locale.api.php	Allow modules to react to language settings changes.
hook_node_access	modules/node/node.api.php	Control access to a node.
hook_node_access_records	modules/node/node.api.php	Set permissions for a node to be written to the database.
hook_node_access_records_alter	modules/node/node.api.php	Alter permissions for a node before it is written to the database.
hook_node_delete	modules/node/node.api.php	Respond to node deletion.
hook_node_grants	modules/node/node.api.php	Inform the node access system what permissions the user has.
hook_node_grants_alter	modules/node/node.api.php	Alter user access rules when trying to view, edit or delete a node.
hook_node_info	modules/node/node.api.php	Define module-provided node types.
hook_node_insert	modules/node/node.api.php	Respond to creation of a new node.
hook_node_load	modules/node/node.api.php	Act on nodes being loaded from the database.
hook_node_operations	modules/node/node.api.php	Add mass node operations.
hook_node_prepare	modules/node/node.api.php	Act on a node object about to be shown on the add/edit form.
hook_node_prepare_translation	modules/node/node.api.php	Act on a node object being cloned for translation.
hook_node_presave	modules/node/node.api.php	Act on a node being inserted or updated.
hook_node_revision_delete	modules/node/node.api.php	Respond to deletion of a node revision.
hook_node_search_result	modules/node/node.api.php	Act on a node being displayed as a search result.
hook_node_type_delete	modules/node/node.api.php	Respond to node type deletion.
hook_node_type_insert	modules/node/node.api.php	Respond to node type creation.
hook_node_type_update	modules/node/node.api.php	Respond to node type updates.
hook_node_update	modules/node/node.api.php	Respond to updates to a node.
hook_node_update_index	modules/node/node.api.php	Act on a node being indexed for searching.
hook_node_validate	modules/node/node.api.php	Perform node validation before a node is created or updated.
hook_node_view	modules/node/node.api.php	Act on a node that is being assembled before rendering.
hook_node_view_alter	modules/node/node.api.php	Alter the results of node_view().
hook_openid	modules/openid/openid.api.php	Allow modules to modify the OpenID request parameters.
hook_openid_discovery_method_info	modules/openid/openid.api.php	Allow modules to declare OpenID discovery methods.
hook_openid_discovery_method_info_alter	modules/openid/openid.api.php	Allow modules to alter discovery methods.
hook_openid_normalization_method_info	modules/openid/openid.api.php	Allow modules to declare OpenID normalization methods.
hook_openid_normalization_method_info_alter	modules/openid/openid.api.php	Allow modules to alter normalization methods.
hook_openid_response	modules/openid/openid.api.php	Allow modules to act upon a successful OpenID login.
hook_overlay_child_initialize	modules/overlay/overlay.api.php	Allow modules to act when an overlay child window is initialized.
hook_overlay_parent_initialize	modules/overlay/overlay.api.php	Allow modules to act when an overlay parent window is initialized.
hook_page_alter	modules/system/system.api.php	Perform alterations before a page is rendered.
hook_page_build	modules/system/system.api.php	Add elements to a page before it is rendered.
hook_page_delivery_callback_alter	modules/system/system.api.php	Alters the delivery callback used to send the result of the page callback to the browser.
hook_path_delete	modules/path/path.api.php	The path has been deleted.
hook_path_insert	modules/path/path.api.php	The path has been inserted.
hook_path_update	modules/path/path.api.php	The path has been updated.
hook_permission	modules/system/system.api.php	Define user permissions.
hook_prepare	modules/node/node.api.php	Act on a node object about to be shown on the add/edit form.
hook_query_alter	modules/system/system.api.php	Perform alterations to a structured query.
hook_query_TAG_alter	modules/system/system.api.php	Perform alterations to a structured query for a given tag.
hook_ranking	modules/node/node.api.php	Provide additional methods of scoring for core search results for nodes.
hook_rdf_mapping	modules/rdf/rdf.api.php	Allow modules to define RDF mappings for field bundles.
hook_rdf_namespaces	modules/rdf/rdf.api.php	Allow modules to define namespaces for RDF mappings.
hook_registry_files_alter	modules/system/system.api.php	Perform necessary alterations to the list of files parsed by the registry.
hook_requirements	modules/system/system.api.php	Check installation requirements and do status reporting.
hook_schema	modules/system/system.api.php	Define the current version of the database schema.
hook_schema_alter	modules/system/system.api.php	Perform alterations to existing database schemas.
hook_search_access	modules/search/search.api.php	Define access to a custom search routine.
hook_search_admin	modules/search/search.api.php	Add elements to the search settings form.
hook_search_execute	modules/search/search.api.php	Execute a search for a set of key words.
hook_search_info	modules/search/search.api.php	Define a custom search type.
hook_search_page	modules/search/search.api.php	Override the rendering of search results.
hook_search_preprocess	modules/search/search.api.php	Preprocess text for search.
hook_search_reset	modules/search/search.api.php	Take action when the search index is going to be rebuilt.
hook_search_status	modules/search/search.api.php	Report the status of indexing.
hook_shortcut_default_set	modules/shortcut/shortcut.api.php	Return the name of a default shortcut set for the provided user account.
hook_simpletest_alter	modules/simpletest/simpletest.api.php	Alter the list of tests.
hook_stream_wrappers	modules/system/system.api.php	Registers PHP stream wrapper implementations associated with a module.
hook_stream_wrappers_alter	modules/system/system.api.php	Alters the list of PHP stream wrapper implementations.
hook_system_info_alter	modules/system/system.api.php	Alter the information parsed from module and theme .info files
hook_system_themes_page_alter	modules/system/system.api.php	Alters theme operation links.
hook_taxonomy_term_delete	modules/taxonomy/taxonomy.api.php	Respond to the deletion of taxonomy terms.
hook_taxonomy_term_insert	modules/taxonomy/taxonomy.api.php	Act on taxonomy terms when inserted.
hook_taxonomy_term_load	modules/taxonomy/taxonomy.api.php	Act on taxonomy terms when loaded.
hook_taxonomy_term_update	modules/taxonomy/taxonomy.api.php	Act on taxonomy terms when updated.
hook_taxonomy_vocabulary_delete	modules/taxonomy/taxonomy.api.php	Respond to the deletion of taxonomy vocabularies.
hook_taxonomy_vocabulary_insert	modules/taxonomy/taxonomy.api.php	Act on taxonomy vocabularies when inserted.
hook_taxonomy_vocabulary_load	modules/taxonomy/taxonomy.api.php	Act on taxonomy vocabularies when loaded.
hook_taxonomy_vocabulary_update	modules/taxonomy/taxonomy.api.php	Act on taxonomy vocabularies when updated.
hook_test_finished	modules/simpletest/simpletest.api.php	An individual test has finished.
hook_test_group_finished	modules/simpletest/simpletest.api.php	A test group has finished.
hook_test_group_started	modules/simpletest/simpletest.api.php	A test group has started.
hook_theme	modules/system/system.api.php	Register a module (or theme's) theme implementations.
hook_theme_registry_alter	modules/system/system.api.php	Alter the theme registry information returned from hook_theme().
hook_tokens	modules/system/system.api.php	Provide replacement values for placeholder tokens.
hook_token_info	modules/system/system.api.php	Provide metadata about available placeholder tokens and token types.
hook_token_info_alter	modules/system/system.api.php	Alter the metadata about available placeholder tokens and token types.
hook_translated_menu_link_alter	modules/menu/menu.api.php	Alter a menu link after it's translated, but before it's rendered.
hook_trigger_info	modules/trigger/trigger.api.php	Declares triggers (events) for users to assign actions to.
hook_uninstall	modules/system/system.api.php	Remove any information that the module sets.
hook_update	modules/node/node.api.php	Respond to updates to a node.
hook_update_dependencies	modules/system/system.api.php	Return an array of information about module update dependencies.
hook_update_index	modules/search/search.api.php	Update the search index for this module.
hook_update_last_removed	modules/system/system.api.php	Return a number which is no longer available as hook_update_N().
hook_update_N	modules/system/system.api.php	Perform a single update.
hook_update_projects_alter	modules/update/update.api.php	Alter the list of projects before fetching data and comparing versions.
hook_update_status_alter	modules/update/update.api.php	Alter the information about available updates for projects.
hook_upgrades	sites/all/modules/coder/coder_upgrade/coder_upgrade.api.php	Declare upgrade sets for an API (or set of APIs).
hook_url_inbound_alter	modules/system/system.api.php	Alters inbound URL requests.
hook_url_outbound_alter	modules/system/system.api.php	Alters outbound URLs.
hook_username_alter	modules/system/system.api.php	Alter the username that is displayed for a user.
hook_user_cancel	modules/user/user.api.php	Act on user account cancellations.
hook_user_cancel_methods_alter	modules/user/user.api.php	Modify account cancellation methods.
hook_user_categories	modules/user/user.api.php	Retrieve a list of all user setting/information categories.
hook_user_delete	modules/user/user.api.php	Respond to user deletion.
hook_user_insert	modules/user/user.api.php	A user account was created.
hook_user_load	modules/user/user.api.php	Act on user objects when loaded from the database.
hook_user_login	modules/user/user.api.php	The user just logged in.
hook_user_logout	modules/user/user.api.php	The user just logged out.
hook_user_operations	modules/user/user.api.php	Add mass user operations.
hook_user_presave	modules/user/user.api.php	A user account is about to be created or updated.
hook_user_role_delete	modules/user/user.api.php	Inform other modules that a user role has been deleted.
hook_user_role_insert	modules/user/user.api.php	Inform other modules that a user role has been added.
hook_user_role_update	modules/user/user.api.php	Inform other modules that a user role has been updated.
hook_user_update	modules/user/user.api.php	A user account was updated.
hook_user_view	modules/user/user.api.php	The user's account information is being displayed.
hook_user_view_alter	modules/user/user.api.php	The user was built; the module may modify the structured content.
hook_validate	modules/node/node.api.php	Perform node validation before a node is created or updated.
hook_view	modules/node/node.api.php	Display a node.
hook_watchdog	modules/system/system.api.php	Log an event message
hook_xmlrpc	modules/system/system.api.php	Register XML-RPC callbacks.
hook_xmlrpc_alter	modules/system/system.api.php	Alter the definition of XML-RPC methods before they are called.
module_hook	includes/module.inc	Determine whether a module implements a hook.
module_hook_info	includes/module.inc	Retrieve a list of what hooks are explicitly declared.
module_implements	includes/module.inc	Determine which modules are implementing a hook.
module_implements_write_cache	includes/module.inc	Writes the hook implementation cache.
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.