Custom module and theme development in Drupal7

Custom Module & Theme
Development in Drupal 7
By: Muhammad Arif
Usman Rehman

Best Configuration
Recommended best practice configuration: PHP5, MySQL 5.x,
Apache 2.x

Best Configuration
Web server: Apache is recommended.
PHP: Drupal requires PHP 4 (4.3.5 or greater) or PHP 5. Drupal core can work with PHP4
but most of contributed modules requires PHP5.
Databases: can be either MySQL or PostgreSQL.The Apache web server and MySQL
database are recommended.
Other web server and database combinations: such as IIS and PostgreSQL have been
tested to a lesser extent.
More information can be found at: http://drupal.org/requirements

Popular Issues
Memory limit: Drupal consumes more memory than other sources.Therefore,
you need have to increase memory limit for Drupal.
Clean URL: To use "Clean URLs" feature on an Apache web server, you will need
the mod_rewrite module and the access permission to local .htaccess files.
PHP: In rare cases, your hosting provides PHP4. Although Drupal can still runs
with PHP 4.3.5, but many contributed modules will not work properly with PHP4.
So you should ensure your PHP version is 5 and above.

The building components of Drupal

Module Types
 Core Modules
 Contributed Modules
 Custom Modules

Core Modules
 Ships with a Standard Drupal Release
 There are Core Optional and Core Required modules
For example:
Node => /admin/structure/types
User => /admin/config/people
Block => /admin/structure/block
System => /admin/config/system
Filter => /admin/config/content/formats
Menu => /admin/structure/menu

Contributed Modules
Over 14,297 free community- contributed modules, known as contributed modules,
are available to
1. Alter and extend Drupal's core capabilities
2. Add new features
3. Customize site's behavior and appearance

Custom Module
1. Local to your Drupal Project
2. Not yet contributed to the contributed repository

Custom Module(When to write)
You need to answer few questions before writing a Custom Module
1. What do you want to achieve by this custom module?
2. Did you search the Contrib Repository to see if a module is already available for
that feature?
3. Have you enabled all possible Configurations of the Core & Contrib module to
check if they offer you the feature you require?
.If your answer is,“Yes, I have done enough research and am sure I have to write
the code now”, then go ahead ....

Custom Module(Why to write)
I have 2 reasons to write a Custom module
1. I need a new feature which is not yet available in Drupal, and probably can be
contributed as a Contrib Module.
2. I don't want to keep adding additional modules to my site for small tweaks, which I can
manage in only one custom module for my website. Don't be too much dependent on
Contribs.
3. Performance.
– Good modules are abstract
– Abstraction can be slow
– Slow is bad
– Custom tailored code can be faster

Module Architecture
 “The building blocks of a module”
Optional Optional

.info File
 name = Event Management
 description = Event Management Module.
 package = Custom
 version = VERSION
 core = 7.x

.install file
 function event_schema()
 function event_install()
 function event_uninstall()

.module file
 Hooks
 Menus
 Includes

.inc file
 Helper functions
 Helper classes

Template(.tpl.php) files
 Include view layer
 HTML

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.
 https://api.drupal.org/api/drupal/includes!module.inc/group/hooks/7

hook_boot
 Perform setup tasks for all page requests.
 This hook is run at the beginning of the page request.
 It is typically used to set up global parameters that are needed later in the request.

hook_init
 Perform setup tasks for non-cached page requests.
 This hook is run at the beginning of the page request.
 It is typically used to set up global parameters that are needed later in the request.
When this hook is called, the theme and all modules are already loaded in
memory.
 This hook is not run on cached pages.

hook_menu
 Define menu items and page callbacks.
 This hook enables modules to register paths in order to define how URL requests
are handled.
 Paths may be registered for URL handling only, or they can register a link to be
placed in a menu (usually the Navigation menu).
 A path and its associated information is commonly called a "menu router item".
This hook is rarely called (for example, when modules are enabled), and its results
are cached in the database.

hook_menu
 Each menu item has a key corresponding to the Drupal path being registered.
 The corresponding array value is an associative array that may contain the following key-value pairs.
1. "title": Required.The untranslated title of the menu item.
2. "description":The untranslated description of the menu item.
3. "page callback":The function to call to display a web page when the user visits the path. If
omitted, the parent menu item's callback will be used instead.
4. "delivery callback":The function to call to package the result of the page callback function and
send it to the browser.
5. "file": A file that will be included before the page callback is called;
.https://api.drupal.org/api/drupal/modules!system!system.api.php/function/hook_menu/7

hook_menu
 "type": A bitmask of flags describing properties of the menu item. Many shortcut
bitmasks are provided as constants in menu.inc:
 MENU_NORMAL_ITEM: Normal menu items show up in the menu tree and can
be moved/hidden by the administrator. Use this for most menu items. It is the
default value if no menu item type is specified.
 MENU_CALLBACK: Callbacks simply register a path so that the correct function
is fired when the url/path is accessed.

Node
 All content on a Drupal website is stored and treated as "nodes".
 A node is any posting, such as a page, poll, article, forum topic, or blog entry.
 Comments are not stored as nodes but are always tied to one.
 Treating all content as nodes allows the flexibility of creating new types of content.
 It also allows you to painlessly apply new features or changes to all content.
 https://drupal.org/documentation/modules/node

Node api
 https://api.drupal.org/api/drupal/modules!node!node.api.php/7

Hook_node_insert
 Respond to creation of a new node.
 This hook is invoked from node_save() after the database query that will insert the
node into the node table is scheduled for execution, after the type-specific
hook_insert() is invoked, and after field_attach_insert() is called.
 https://api.drupal.org/api/drupal/modules!node!
node.api.php/group/node_api_hooks/7

Hook_node_update
 Respond to updates to a node.
 This hook is invoked from node_save() after the database query that will update
node in the node table is scheduled for execution, after the type-specific
hook_update() is invoked, and after field_attach_update() is called.

Hook_node_delete
 Respond to node deletion.
 This hook is invoked from node_delete_multiple() after the type-specific
hook_delete() has been invoked, but before hook_entity_delete and
field_attach_delete() are called, and before the node is removed from the node
table in the database.

Form APi
 Functions to enable the processing and display of HTML forms.
 Drupal uses these functions to achieve consistency in its form processing and
presentation, while simplifying code and reducing the amount of HTML that must
be explicitly generated by modules.
 https://api.drupal.org/api/drupal/developer!topics!forms_api_reference.html/7

Create Form
 The process for creating a form is mainly two steps.
1. The first is to build an associative array $form that contains all the fields.
2. The second step is to return that $form variable.

Form Attributes

Create Form
 It is important to note that the function takes the inputs $form, and a reference
&$form_state.
 This function will be called when Drupal tries to build the form
"form_example_form.“

Validate and submit form
 Now that we have a form, we need to add two more function:
1. form_example_form_validate, and
2. form_example_form_submit.
.These two functions are hook functions that will be called when Drupal validates
the form and when it submits the form (assuming it validated).
.These two functions need to named similar to the other form, but with "validate"
and "submit" at the end.

$form and $form_State
 You will note that these three functions take the same variables.
1. $form is the original form information and can be seen as the original structure
of the form.
2. $form_state holds all of the submitted values as well as other information, some
of which you can add yourself.

Show form
 We want to see the form!!!
1. We will add a menu link to this form.
2. Show form in a Block

What to do when your form is submitted?
 From this point, you will want to either
1. save the form data,
2. send an email, or
3. display some information.

Form references
 https://api.drupal.org/api/drupal/includes!form.inc/group/form_api/7
 https://drupal.org/node/1419390

Alter Form
 Perform alterations before a form is rendered.
 One popular use of this hook is to add form elements to the node form.
 When altering a node form, the node object can be accessed at $form['#node'].
 https://api.drupal.org/api/drupal/modules!system!
system.api.php/function/hook_form_alter/7

Ajax in Form
Drupal supports ajax in forms
Example
https://api.drupal.org/api/examples/ajax_example!ajax_example.module/7

Working with Javascript

Database API
 The Drupal 7 Database API provides a standard, vendor-agnostic abstraction layer
for accessing database servers.

Database abstraction layer
 Allow the use of different database servers using the same code base.
 Most Drupal database SELECT queries are performed by a call to db_query() or
db_query_range()
 For example, one might wish to return a list of the most recent 10 nodes authored
by a given user. Instead of directly issuing the SQL query
SELECT n.nid, n.title, n.created FROM noden WHERE n.uid = $uid LIMIT 0, 10;
one would instead call the Drupal functions:
$result = db_query_range('SELECT n.nid, n.title, n.created
FROM {node} n WHERE n.uid = :uid', 0, 10, array(':uid' => $uid));
foreach ($result as$record) {
// Perform operationson $record->title, etc. here.
}

Db_select()
 https://api.drupal.org/api/drupal/includes!database!
database.inc/function/db_select/7

Transactions
function my_transaction_function() {
// Thetransaction openshere.
$txn = db_transaction(); try {
// Your codehere.
} catch (Exception $e) {
// Something went wrong somewhere, so roll back
now.
$txn->rollback();
// Log theexception to watchdog.
watchdog_exception('type', $e);
}
https://api.drupal.org/api/drupal/includes!database!database.inc/group/database/7

Web Services
 Create a Menu
 Menu “delivery_callback” should be => ‘ajax_deliver’
 Write drupal_exit() at end of menu function
 Flush cache

Theming in drupal
 The first step is that logic must be separated as much as possible from presentation.
 To accomplish this, modules do as much of the work on the data as possible, and
hand that data off to the presentation layer.
 This is handled through the theme() function.

Theming
 Register theme hooks
 Implement theme functions
 Implement default templates
 https://api.drupal.org/api/drupal/modules!system!
system.api.php/function/hook_theme/7

Theme Hook
 Register a module (or theme's) theme implementations.
 Every chunk of output that is themed through the theme() function is called a theme
hook.
 In order to utilize a theme hook, your module first has to register that this exists.

Implement theme functions
Drupal allows you to use functions for your default theme implementations.
This is somewhat faster performance than loading template files.
New in Drupal 7, theme functions can have preprocess functions just like templates.
Copying and modifying template files is still considered more friendly for themers.
Theme functions are named by prepending 'theme_' to the name of the hook.
The arguments given to theme('hook') will be passed straight through, unaltered.

Implement theme functions
 Example.

Implement default templates
 When implemented as a template, the .tpl.php file is required.
 It should be in the same directory as the .module file (though the 'path' directive
can be used to place these templates in another directory or a sub-directory).
 Templates should be as much pure HTML as possible, but there are a few functions
that are explicitly encouraged in your templates:
1. t(): modules should always provide proper translatability, and templates are no
exception.
2. format_date(): since this function is, really, a presentation function, the presentation
layer is the appropriate place for it.

Implement default templates
Example

Performance: Reduce # of HTTP Requests
Problem:
 80% of the end-user response time is spent on the front-end.
 Most of this time is tied up in downloading all the components (images, style-
sheets, scripts, Flash) in the page.
 Reducing the number of components in turn reduces the number of HTTP requests
required to render the page.This is the key to faster pages.
Solution:
 Turn on Bandwidth optimizations for CSS and JavaScript files Manual CSS sprite
generator
 Go for Bootstrap
 Use Yslow firefox plugin

Performance: Cache
Caching using Boost
 Extension of Performance module
 Instead of caching results in tables, stores them in files bypassing PHP and MySQL
 Limited to anonymous visitors – Not for sites with high number of authenticated
visitors
How it works:
 Uses apache mod_rewrite directives in .htacess to check if GET
 Logged in cookie does not exist
 HTML file cached on file-system

3. Create Install File and Module Schema

Custom module and theme development in Drupal7

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