Drupal: Minimum Hooks to Develop Your Own Module (English)

Obviously there is a learning curve to overcome in order to understand a concept of a world of a Drupal's hook system, that is, a.k.a callbacks. The following is a summary of hooks both for a management system and a form system, which I organized.

Hooks for a Management

• hook_help($section)

  The implementation of hook_help is also recommended even though those are described in yourmodule.info since Drupal 5.x

• hook_perm()

  A set of three hooks such as hook_perm, hook_access and hook_menu should be always implemented together. It must be implemented in order to set access controls in every single user group at Home > Administer > Access Control

• hook_access($op, $node)

  Describes which access privilege is bound to the corresponding operation, which is an argument of this function, such as $op == 'create'、$op == 'update'、$op == 'delete', and etc.

• hook_menu($may_cache)

  Maps a set of the path, module, privilege and page tile in this hook.

  'type' => MENU_NORMAL_ITEM enables the item to show in the menu system

  'type' => MENU_CALLBACK disables the item to show in the menu system and only to call the mapped function with the path.

• hook_node_info()

  The following description enables two forms in one module. The significant lines are 'module' => 'form1' and 'module' => 'form1'; eventually they turn out the function name such as form1_view, form2_view which are used as the prefix such as form1_ or form2_ with hooks for forms on the later explanation.
  

  <?php

function hook_node_info() {
  return array(

    'form1' => array(
             'name'        => t('form1'),
             'module'      => 'form1',
             'description' => t("Describe the explanation of form1"),
    ),

    'form2' => array(
             'name'        => t('form2'),
             'module'      => 'form2',
             'description' => t("Describe the explanation of form2"),
    )
  );
}

?>

• hook_admin()

  Enables the configurable values in this module to setup under the menu such as Home > Administer > Site Configuration > Your Module Settings

Hooks for a Form
Renders a page or shows a form

• hook_form(&$node)

  Display a form to input data

• hook_validate($form_id, $form_values)

  Allows the inputted values to check when a submit button is pressed; you can make an error page show when the valus are invalid strings or out of the range by calling form_set_error('Write the field name of the item here', t('Write an error description here'));

• hook_submit($node)

  Called before hook_insert is called when a submit button is pressed. And also allows $node that should be passed to hook_insert to alter

• hook_insert($node)

  Receives values from an inputting form (that is, just a 'form') and stores a record (that is, a node) into the database. Virtually, An SQL statement 'INSERT' will be issued in this hook. As a result, a new node will be added into the database.

• hook_update($node)

  Receives values from an edit form (that is, just a 'form') and updates a record (that is, a node) in the database. Virtually, An SQL statement 'UPDATE' will be issued in this hook.

• hook_delete(&$node)

  Called when a Delete button is pressed as the same as an edit form (that is, just a 'form'). A node stored in a database is deleted. Virtually, An SQL statement 'DELETE' will be issued in this hook.

• hook_load($node)

  In Drupal, each document created by a user is stored into 'node' table with a unit 'node'. If you add a custom field into 'node', you must explicitly specify your custom field and load the node when your module is about to show the node. The code is the following.
  

  <?php

function hook_load($node) {

  $r = db_fetch_object(
           db_query('SELECT `your_id`, `your_field1`, `your_field2`, ... FROM {your_table_name} WHERE nid = %d', $node->nid)
        );

  return $r;
}

?>

• hook_prepare(&$node)

  Allows node vales to edit before calling hook_view. For example, if you show a date formatted to mm/dd/yyyy before calling hook_view, you can make the date format in this funciton.

• hook_view(&$node, $teaser = FALSE, $page = FALSE)

  Display a node. If you implement 'yourmodule_prepare', it should be called at the beginning of this hook implementation.
  

  <?php

function hook_view(&$node, $teaser = FALSE, $page = FALSE) {

  $node = node_prepare($node, $teaser);
  yourmodule_prepare($node);

  ...

}

?>