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
custom_url_rewrite_inbound	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	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...
EMMODULE_PROVIDER_content_generate	contrib/emfield/hooks/emfield.php	Generate random media for the devel module.
EMMODULE_PROVIDER_embedded_link	contrib/emfield/hooks/emfield.php	Returns a link to view the original media at the provider's site.
EMMODULE_PROVIDER_emfield_submenu	contrib/emfield/hooks/emfield.php	Returns any menu pages required by this provider.
EMMODULE_PROVIDER_emfield_subtheme	contrib/emfield/hooks/emfield.php	Returns any theme functions required for this provider.
EMMODULE_PROVIDER_extract	contrib/emfield/hooks/emfield.php	Parse the URL or embed code provided by an editor.
EMMODULE_PROVIDER_form	contrib/emfield/hooks/emfield.php	Allow a provider to add its own elements to the content creation form.
EMMODULE_PROVIDER_info	contrib/emfield/hooks/emfield.php	Return the information about a specific provider.
EMMODULE_PROVIDER_submenu	contrib/emfield/hooks/emfield.php	@TODO Not sure why this is there -- provided for already w/ hook_emfield_submenu.
EMMODULE_PROVIDER_subtheme	contrib/emfield/hooks/emfield.php	@TODO Not sure why this is there -- provided for already w/ hook_emfield_subtheme.
EMMODULE_PROVIDER_validate	contrib/emfield/hooks/emfield.php	Validate the provider's embedded code.
hook_access	hooks/node.php	Define access restrictions.
hook_actions_delete	hooks/core.php	Execute code after an action is deleted.
hook_action_info	hooks/core.php	Declare information about one or more Drupal actions.
hook_action_info_alter	hooks/core.php	Alter the actions declared by another module.
hook_add_to_cart	contrib/ubercart/docs/hooks.php	Do extra processing when an item is added to the shopping cart.
hook_add_to_cart_data	contrib/ubercart/docs/hooks.php	Add extra information to a cart item's "data" array.
hook_block	hooks/core.php	Declare a block or set of blocks.
hook_boot	hooks/core.php	Perform setup tasks. See also, hook_init.
hook_calculate_tax	contrib/ubercart/docs/hooks.php	Calculate tax line items for an order.
hook_cart_display	contrib/ubercart/docs/hooks.php	Control the display of an item in the cart.
hook_cart_item	contrib/ubercart/docs/hooks.php	Add extra data about an item in the cart.
hook_cart_pane	contrib/ubercart/docs/hooks.php	Register callbacks for a cart pane.
hook_checkout_pane	contrib/ubercart/docs/hooks.php	Register callbacks for a checkout pane.
hook_comment	hooks/core.php	Respond to comment actions.
hook_cron	hooks/core.php	Perform periodic actions.
hook_db_rewrite_sql	hooks/core.php	Rewrite database queries, usually for access control.
hook_delete	hooks/node.php	Respond to node deletion.
hook_disable	hooks/install.php	Perform necessary actions before module is disabled.
hook_download_authorize	contrib/ubercart/docs/hooks.php	Give clearance to a user to download a file.
hook_elements	hooks/core.php	Allows modules to declare their own Forms API element types and specify their default values.
hook_emfield_data_alter	contrib/emfield/hooks/emfield.php	Alter the data array of a media item before it is stored in the database.
hook_emfield_field_columns_extra	contrib/emfield/hooks/emfield.php	Generally used for metadata, this will add an array of database column information to be saved when present in the field. Note that this hook is used to return columns to be saved for all Embedded Media Fields, and is currently unused by the core...
hook_emfield_providers	contrib/emfield/hooks/emfield.php	Build a list of provider files that serve the invoking module.
hook_emfield_widget_extra	contrib/emfield/hooks/emfield.php	This passes on the original implementation of CCK's hook_widget.
hook_emfield_widget_settings_extra	contrib/emfield/hooks/emfield.php	This passes on the original implementation of CCK's hook_widget_settings.
hook_enable	hooks/install.php	Perform necessary actions after module is enabled.
hook_exit	hooks/core.php	Perform cleanup tasks.
hook_file_action	contrib/ubercart/docs/hooks.php	Perform actions on file products.
hook_file_download	hooks/core.php	Control access to private file downloads and specify HTTP headers.
hook_file_transfer_alter	contrib/ubercart/docs/hooks.php	Make changes to a file before it is downloaded by the customer.
hook_filter	hooks/core.php	Define content filters.
hook_filter_tips	hooks/core.php	Provide tips for using filters.
hook_flush_caches	hooks/core.php	Add a list of cache tables to be cleared.
hook_footer	hooks/core.php	Insert closing HTML.
hook_form	hooks/node.php	Display a node editing form.
hook_forms	hooks/core.php	Map form_ids to builder functions.
hook_form_alter	hooks/core.php	Perform alterations before a form is rendered.
hook_form_FORM_ID_alter	hooks/core.php	Provide a form-specific alteration instead of the global hook_form_alter().
hook_gmap	contrib/gmap/gmap.php	Change the way gmap works.
hook_help	hooks/core.php	Provide online user help.
hook_hook_info	hooks/core.php	Expose a list of triggers (events) that users can assign actions to. See alsohook_action_info(), which allows your module to define actions.
hook_imagecache_actions	contrib/imagecache/imagecache.api.php	Inform ImageCache about actions that can be performed on an image.
hook_imagecache_default_presets	contrib/imagecache/imagecache.api.php	Provides default ImageCache presets that can be overridden by site administrators.
hook_init	hooks/core.php	Perform setup tasks. See also, hook_boot.
hook_insert	hooks/node.php	Respond to node insertion.
hook_install	hooks/install.php	Install the current version of the database schema, and any other setup tasks.
hook_line_item	contrib/ubercart/docs/hooks.php	Used to define line items that are attached to orders.
hook_line_item_alter	contrib/ubercart/docs/hooks.php	Alter a line item on an order when the order is loaded.
hook_line_item_data_alter	contrib/ubercart/docs/hooks.php	Alter the line item definitions declared in hook_line_item().
hook_link	hooks/core.php	Define internal Drupal links.
hook_link_alter	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	hooks/node.php	Load node-type-specific information.
hook_locale	hooks/core.php	Allows modules to define their own text groups that can be translated.
hook_mail	hooks/core.php	Prepare a message based on parameters; called from drupal_mail().
hook_mail_alter	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	hooks/core.php	Define menu items and page callbacks.
hook_menu_alter	hooks/core.php	Alter the data being saved to the {menu_router} table after hook_menu is invoked.
hook_menu_link_alter	hooks/core.php	Alter the data being saved to the {menu_links} table by menu_link_save().
hook_nodeapi	hooks/core.php	Act on nodes defined by other modules.
hook_node_access_records	hooks/core.php	Set permissions for a node to be written to the database.
hook_node_grants	hooks/core.php	Inform the node access system what permissions the user has.
hook_node_info	hooks/node.php	Define module-provided node types.
hook_node_operations	hooks/core.php	Add mass node operations.
hook_node_type	hooks/node.php	Act on node type changes.
hook_order	contrib/ubercart/docs/hooks.php	Perform actions on orders.
hook_order_actions	contrib/ubercart/docs/hooks.php	Add links to local tasks for orders on the admin's list of orders.
hook_order_pane	contrib/ubercart/docs/hooks.php	Register callbacks for an order pane.
hook_order_product_alter	contrib/ubercart/docs/hooks.php	Allows modules to alter ordered products when they're loaded with an order.
hook_order_state	contrib/ubercart/docs/hooks.php	Register static order states.
hook_payment_gateway	contrib/ubercart/docs/hooks.php	Register payment gateway callbacks. See also
hook_payment_method	contrib/ubercart/docs/hooks.php	Register callbacks for payment methods.
hook_perm	hooks/core.php	Define user permissions.
hook_ping	hooks/core.php	Ping another server.
hook_prepare	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_product_class	contrib/ubercart/docs/hooks.php	Perform actions on product classes.
hook_product_description	contrib/ubercart/docs/hooks.php	Return a structured array representing the given product's description.
hook_product_description_alter	contrib/ubercart/docs/hooks.php	Alters the given product description.
hook_product_types	contrib/ubercart/docs/hooks.php	List node types which should be considered products.
hook_profile_alter	hooks/core.php	Alter profile items before they are rendered.
hook_requirements	hooks/install.php	Check installation requirements and do status reporting.
hook_schema	hooks/install.php	Define the current version of the database schema.
hook_schema_alter	hooks/core.php	Perform alterations to existing database schemas.
hook_search	hooks/core.php	Define a custom search routine.
hook_search_preprocess	hooks/core.php	Preprocess text for the search index.
hook_shipment	contrib/ubercart/docs/hooks.php	Handle additional data for shipments.
hook_shipping_method	contrib/ubercart/docs/hooks.php	Define callbacks and service options for shipping methods.
hook_shipping_type	contrib/ubercart/docs/hooks.php	Define shipping types for shipping methods.
hook_store_status	contrib/ubercart/docs/hooks.php	Add status messages to the "Store administration" page.
hook_system_info_alter	hooks/core.php	Alter the information parsed from module and theme .info files
hook_tapir_table_alter	contrib/ubercart/docs/hooks.php	Allow modules to alter the TAPIr table after the rows are populated.
hook_tapir_table_header_alter	contrib/ubercart/docs/hooks.php	Allow modules to alter TAPIr table headers.
hook_taxonomy	hooks/core.php	Act on taxonomy changes.
hook_term_path	hooks/core.php	Allows modules to provide an alternative path for the terms it manages.
hook_theme	hooks/core.php	Register a module (or theme's) theme implementations.
hook_theme_registry_alter	hooks/core.php	Alter the theme registry information returned from hook_theme().
hook_translated_menu_link_alter	hooks/core.php	Alter a menu link after it's translated, but before it's rendered.
hook_translation_link_alter	hooks/core.php	Perform alterations on translation links.
hook_ucga_display	contrib/ubercart/docs/hooks.php	Used to determine whether or not UC Google Analytics should add e-commerce tracking code to the bottom of the page.
hook_ucga_item_alter	contrib/ubercart/docs/hooks.php	Allows modules to alter items before they're added to the UC Google Analytics e-commerce tracking code.
hook_ucga_trans_alter	contrib/ubercart/docs/hooks.php	Allows modules to alter transaction info before it's added to the UC Google Analytics e-commerce tracking code.
hook_uc_checkout_complete	contrib/ubercart/docs/hooks.php	Take action when checkout is completed.
hook_uc_form_alter	contrib/ubercart/docs/hooks.php	Allow modules to modify forms before Drupal invokes hook_form_alter().
hook_uc_message	contrib/ubercart/docs/hooks.php	Convenience function to display large blocks of text in several places.
hook_uc_payment_entered	contrib/ubercart/docs/hooks.php	Take action when a payment is entered for an order.
hook_uc_price_handler	contrib/ubercart/docs/hooks.php	Use this hook to define price handlers for your module. You may define one price alterer and one price formatter. You may also define options that are merged into the options array in order of each price alterer's weight.
hook_uc_product_models	contrib/ubercart/docs/hooks.php	Notify core of any SKUs your module adds to a given node.
hook_uc_stock_adjusted	contrib/ubercart/docs/hooks.php	Allow modules to take action when a stock level is changed.
hook_uninstall	hooks/install.php	Remove any tables or variables that the module sets.
hook_update	hooks/node.php	Respond to node updating.
hook_update_cart_item	contrib/ubercart/docs/hooks.php	Handle requests to update a cart item.
hook_update_index	hooks/core.php	Update Drupal's full-text index for this module.
hook_update_last_removed	hooks/install.php	Return a number which is no longer available as hook_update_N().
hook_update_N	hooks/install.php	Perform a single update.
hook_update_projects_alter	hooks/core.php	Alter the list of projects before fetching data and comparing versions.
hook_update_status_alter	hooks/core.php	Alter the information about available updates for projects.
hook_user	hooks/core.php	Act on user account actions.
hook_user_operations	hooks/core.php	Add mass user operations.
hook_validate	hooks/node.php	Verify a node editing form.
hook_view	hooks/node.php	Display a node.
hook_watchdog	hooks/core.php	Log an event message
hook_xmlrpc	hooks/core.php	Register XML-RPC callbacks.
module_hook	core/includes/module.inc	Determine whether a module implements a hook.
module_implements	core/includes/module.inc	Determine which modules are implementing a hook.
module_invoke	core/includes/module.inc	Invoke a hook in a particular module.
module_invoke_all	core/includes/module.inc	Invoke a hook in all enabled modules that implement it.