Drupal 7 Module Development

Building an Admin Interface
Each argument in a menu item's path can be accessed as an argument that is
available to be passed to our page callback, starting with 0 for the root argument.
So here the string user is item 0, and the user's ID is item 1. To use the user's ID as a
page callback argument, we reference it by its number. The result in this case is that
the user's ID will be passed as an additional argument to drupal_get_form().
We have one other difference in this second menu item:
'type' => MENU_LOCAL_TASK,
We have defined our type as MENU_LOCAL_TASK. This tells Drupal that our menu
item describes actions that can be performed on the parent item. In this example,
Warn is an action that can be performed on a user. These are usually rendered as an
additional tab on the page in question, as you can see in the following example user
profile screen:
Having defined the paths for our pages through hook_menu(), we now need to build
our forms.
Form API
In standard web development, one of the most tedious and unrewarding tasks is
defining HTML forms and handling their submissions. Lay out the form, create
labels, write the submission function, figure out error handling, and the worst part
is that from site to site much of this code is boilerplate—it's fundamentally the
same, differing only in presentation. Drupal's Form API is a powerful tool allowing
developers to create forms and handle form submissions quickly and easily. This
is done by defining arrays of form elements and creating validation and submit
callbacks for the form.
[ 126 ]