- •Contents at a Glance
- •Contents
- •Foreword
- •About the Authors
- •About the Technical Reviewers
- •Acknowledgments
- •Introduction
- •How Drupal Works
- •What Is Drupal?
- •Technology Stack
- •Core
- •Administrative Interface
- •Modules
- •Hooks
- •Themes
- •Nodes
- •Fields
- •Blocks
- •File Layout
- •Serving a Request
- •The Web Server’s Role
- •The Bootstrap Process
- •Processing a Request
- •Theming the Data
- •Summary
- •Writing a Module
- •Creating the Files
- •Implementing a Hook
- •Adding Module-Specific Settings
- •Defining Your Own Administration Section
- •Presenting a Settings Form to the User
- •Validating User-Submitted Settings
- •Storing Settings
- •Using Drupal’s variables Table
- •Retrieving Stored Values with variable_get()
- •Further Steps
- •Summary
- •Hooks, Actions, and Triggers
- •Understanding Events and Triggers
- •Understanding Actions
- •The Trigger User Interface
- •Your First Action
- •Assigning the Action
- •Changing Which Triggers an Action Supports
- •Actions That Support Any Trigger
- •Advanced Actions
- •Using the Context in Actions
- •How the Trigger Module Prepares the Context
- •Changing Existing Actions with action_info_alter()
- •Establishing the Context
- •How Actions Are Stored
- •The actions Table
- •Action IDs
- •Calling an Action Directly with actions_do()
- •Defining Your Own Triggers with hook_trigger_info()
- •Adding Triggers to Existing Hooks
- •Summary
- •The Menu System
- •Callback Mapping
- •Mapping URLs to Functions
- •Creating a Menu Item
- •Page Callback Arguments
- •Page Callbacks in Other Files
- •Adding a Link to the Navigation Block
- •Menu Nesting
- •Access Control
- •Title Localization and Customization
- •Defining a Title Callback
- •Wildcards in Menu Items
- •Basic Wildcards
- •Wildcards and Page Callback Parameters
- •Using the Value of a Wildcard
- •Wildcards and Parameter Replacement
- •Passing Additional Arguments to the Load Function
- •Special, Predefined Load Arguments: %map and %index
- •Building Paths from Wildcards Using to_arg() Functions
- •Special Cases for Wildcards and to_arg() Functions
- •Altering Menu Items from Other Modules
- •Altering Menu Links from Other Modules
- •Kinds of Menu Items
- •Common Tasks
- •Assigning Callbacks Without Adding a Link to the Menu
- •Displaying Menu Items As Tabs
- •Hiding Existing Menu Items
- •Using menu.module
- •Common Mistakes
- •Summary
- •Working with Databases
- •Defining Database Parameters
- •Understanding the Database Abstraction Layer
- •Connecting to the Database
- •Performing Simple Queries
- •Retrieving Query Results
- •Getting a Single Value
- •Getting Multiple Rows
- •Using the Query Builder and Query Objects
- •Getting a Limited Range of Results
- •Getting Results for Paged Display
- •Other Common Queries
- •Inserts and Updates with drupal_write_record()
- •The Schema API
- •Using Module .install Files
- •Creating Tables
- •Using the Schema Module
- •Field Type Mapping from Schema to Database
- •Textual
- •Varchar
- •Char
- •Text
- •Numerical
- •Integer
- •Serial
- •Float
- •Numeric
- •Date and Time: Datetime
- •Binary: Blob
- •Declaring a Specific Column Type with mysql_type
- •Maintaining Tables
- •Deleting Tables on Uninstall
- •Changing Existing Schemas with hook_schema_alter()
- •Modifying Other Modules’ Queries with hook_query_alter()
- •Connecting to Multiple Databases Within Drupal
- •Using a Temporary Table
- •Writing Your Own Database Driver
- •Summary
- •Working with Users
- •The $user Object
- •Testing If a User Is Logged In
- •Introduction to user hooks
- •Understanding hook_user_view($account, $view_mode)
- •The User Registration Process
- •Using profile.module to Collect User Information
- •The Login Process
- •Adding Data to the $user Object at Load Time
- •Providing User Information Categories
- •External Login
- •Summary
- •Working with Nodes
- •So What Exactly Is a Node?
- •Not Everything Is a Node
- •Creating a Node Module
- •Creating the .install File
- •Creating the .info File
- •Creating the .module File
- •Providing Information About Our Node Type
- •Modifying the Menu Callback
- •Defining Node-Type–Specific Permissions with hook_permission()
- •Limiting Access to a Node Type with hook__node_access()
- •Customizing the Node Form for Our Node Type
- •Validating Fields with hook_validate()
- •Saving Our Data with hook_insert()
- •Keeping Data Current with hook_update()
- •Cleaning Up with hook_delete()
- •Modifying Nodes of Our Type with hook_load()
- •Using hook_view()
- •Manipulating Nodes That Are Not Our Type with hook_node_xxxxx()
- •How Nodes Are Stored
- •Creating a Node Type with Custom Content Types
- •Restricting Access to Nodes
- •Defining Node Grants
- •What Is a Realm?
- •What Is a Grant ID?
- •The Node Access Process
- •Summary
- •Working with Fields
- •Creating Content Types
- •Adding Fields to a Content Type
- •Creating a Custom Field
- •Adding Fields Programmatically
- •Summary
- •The Theme System
- •Themes
- •Installing an Off-the-Shelf Theme
- •Building a Theme
- •The .info File
- •Adding Regions to Your Theme
- •Adding CSS Files to Your Theme
- •Adding JavaScript Files
- •Adding Settings to Your Theme
- •Understanding Template Files
- •The Big Picture
- •The html.php.tpl File
- •The page.tpl.php File
- •The region.tpl.php File
- •The node.tpl.php File
- •The field.tpl.php File
- •The block.tpl.php File
- •Overriding Template Files
- •Other Template Files
- •Introducing the theme() Function
- •An Overview of How theme() Works
- •Overriding Themable Items
- •Overriding with Template Files
- •Adding and Manipulating Template Variables
- •Using the Theme Developer Module
- •Summary
- •Working with Blocks
- •What Is a Block?
- •Block Configuration Options
- •Block Placement
- •Defining a Block
- •Using the Block Hooks
- •Building a Block
- •Enabling a Block When a Module Is Installed
- •Block Visibility Examples
- •Displaying a Block to Logged-In Users Only
- •Displaying a Block to Anonymous Users Only
- •Summary
- •The Form API
- •Understanding Form Processing
- •Initializing the Process
- •Setting a Token
- •Setting an ID
- •Collecting All Possible Form Element Definitions
- •Looking for a Validation Function
- •Looking for a Submit Function
- •Allowing Modules to Alter the Form Before It’s Built
- •Building the Form
- •Allowing Functions to Alter the Form After It’s Built
- •Checking If the Form Has Been Submitted
- •Finding a Theme Function for the Form
- •Allowing Modules to Modify the Form Before It’s Rendered
- •Rendering the Form
- •Validating the Form
- •Token Validation
- •Built-In Validation
- •Element-Specific Validation
- •Validation Callbacks
- •Submitting the Form
- •Redirecting the User
- •Creating Basic Forms
- •Form Properties
- •Form IDs
- •Fieldsets
- •Theming Forms
- •Using #prefix, #suffix, and #markup
- •Using a Theme Function
- •Telling Drupal Which Theme Function to Use
- •Specifying Validation and Submission Functions with hook_forms()
- •Call Order of Theme, Validation, and Submission Functions
- •Writing a Validation Function
- •Form Rebuilding
- •Writing a Submit Function
- •Changing Forms with hook_form_alter()
- •Altering Any Form
- •Altering a Specific Form
- •Submitting Forms Programmatically with drupal_form_submit()
- •Dynamic Forms
- •Form API Properties
- •Properties for the Root of the Form
- •#action
- •#built
- •#method
- •Properties Added to All Elements
- •#description
- •#attributes
- •#required
- •#tree
- •Properties Allowed in All Elements
- •#type
- •#access
- •#after_build
- •#array_parents
- •#attached
- •#default_value
- •#disabled
- •#element_validate
- •#parents
- •#post_render
- •#prefix
- •#pre_render
- •#process
- •#states
- •#suffix
- •#theme
- •#theme_wrappers
- •#title
- •#tree
- •#weight
- •Form Elements
- •Text Field
- •Password
- •Password with Confirmation
- •Textarea
- •Select
- •Radio Buttons
- •Check Boxes
- •Value
- •Hidden
- •Date
- •Weight
- •File Upload
- •Fieldset
- •Submit
- •Button
- •Image Button
- •Markup
- •Item
- •#ajax Property
- •Summary
- •Filters
- •Filters and Text formats
- •Installing a Filter
- •Knowing When to Use Filters
- •Creating a Custom Filter
- •Implementing hook_filter_info()
- •The Process Function
- •Helper Function
- •Summary
- •Searching and Indexing Content
- •Building a Custom Search Page
- •The Default Search Form
- •The Advanced Search Form
- •Adding to the Search Form
- •Introducing the Search Hooks
- •Formatting Search Results with hook_search_page()
- •Making Path Aliases Searchable
- •Using the Search HTML Indexer
- •When to Use the Indexer
- •How the Indexer Works
- •Adding Metadata to Nodes: hook_node_update_index()
- •Indexing Content That Isn’t a Node: hook_update_index()
- •Summary
- •Working with Files
- •How Drupal Serves Files
- •Managed and Unmanaged Drupal APIs
- •Public Files
- •Private Files
- •PHP Settings
- •Media Handling
- •Upload Field
- •Video and Audio
- •File API
- •Database Schema
- •Common Tasks and Functions
- •Finding the Default Files URI
- •Copying and Moving Files
- •Checking Directories
- •Uploading Files
- •Getting the URL for a File
- •Finding Files in a Directory
- •Finding the Temp Directory
- •Neutralizing Dangerous Files
- •Checking Disk Space
- •Authentication Hooks for Downloading
- •Summary
- •Working with Taxonomy
- •The Structure of Taxonomy
- •Creating a Vocabulary
- •Creating Terms
- •Assigning a Vocabulary to a Content Type
- •Kinds of Taxonomy
- •Flat
- •Hierarchical
- •Multiple Hierarchical
- •Viewing Content by Term
- •Using AND and OR in URLs
- •Specifying Depth for Hierarchical Vocabularies
- •Automatic RSS Feeds
- •Storing Taxonomies
- •Module-Based Vocabularies
- •Creating a Module-Based Vocabulary
- •Keeping Informed of Vocabulary Changes with Taxonomy Hooks
- •Common Tasks
- •Displaying Taxonomy Terms Associated with a Node
- •Building Your Own Taxonomy Queries
- •Using taxonomy_select_nodes()
- •Taxonomy Functions
- •Retrieving Information About Vocabularies
- •taxonomy_vocabulary_load($vid)
- •taxonomy_get_vocabularies()
- •Adding, Modifying, and Deleting Vocabularies
- •taxonomy_vocabulary_save($vocabulary)
- •taxonomy_vocabulary_delete($vid)
- •Retrieving Information About Terms
- •taxonomy_load_term($tid)
- •taxonomy_get_term_by_name($name)
- •Adding, Modifying, and Deleting Terms
- •taxonomy_term_save($term)
- •taxonomy_term_delete($tid)
- •Retrieving Information About Term Hierarchy
- •taxonomy_get_parents($tid, $key)
- •taxonomy_get_parents_all($tid)
- •taxonomy_get_children($tid, $vid, $key)
- •taxonomy_get_tree($vid, $parent, $max_depth, $load_entities = FALSE)
- •Finding Nodes with Certain Terms
- •Additional Resources
- •Summary
- •Caching
- •Knowing When to Cache
- •How Caching Works
- •How Caching Is Used Within Drupal Core
- •Menu System
- •Caching Filtered Text
- •Administration Variables and Module Settings
- •Disabling Caching
- •Page Caching
- •Static Page Caching
- •Blocks
- •Using the Cache API
- •Caching Data with cache_set()
- •Retrieving Cached Data with cache_get() and cache_get_multiple()
- •Checking to See If Cache Is Empty with cache_is_empty()
- •Clearing Cache with cache_clear_all()
- •Summary
- •Sessions
- •What Are Sessions?
- •Usage
- •Session-Related Settings
- •In .htaccess
- •In settings.php
- •In bootstrap.inc
- •Requiring Cookies
- •Storage
- •Session Life Cycle
- •Session Conversations
- •First Visit
- •Second Visit
- •User with an Account
- •Common Tasks
- •Changing the Length of Time Before a Cookie Expires
- •Changing the Name of the Session
- •Storing Data in the Session
- •Summary
- •Using jQuery
- •What Is jQuery?
- •How jQuery Works
- •Using a CSS ID Selector
- •Using a CSS Class Selector
- •jQuery Within Drupal
- •Your First jQuery Code
- •Targeting an Element by ID
- •Method Chaining
- •Adding or Removing a Class
- •Wrapping Existing Elements
- •Changing Values of CSS Elements
- •Where to Put JavaScript
- •Adding JavaScript via a Theme .info File
- •A Module That Uses jQuery
- •Overridable JavaScript
- •Building a jQuery Voting Widget
- •Building the Module
- •Using Drupal.behaviors
- •Ways to Extend This Module
- •Compatibility
- •Next Steps
- •Summary
- •Localization and Translation
- •Enabling the Locale Module
- •User Interface Translation
- •Strings
- •Translating Strings with t()
- •Replacing Built-In Strings with Custom Strings
- •String Overrides in settings.php
- •Replacing Strings with the Locale Module
- •Exporting Your Translation
- •Starting a New Translation
- •Generating .pot Files with Translation Template Extractor
- •Creating a .pot File for Your Module
- •Using the Command Line
- •Using the Web-Based Extractor
- •Creating .pot Files for an Entire Site
- •Installing a Language Translation
- •Setting Up a Translation at Install Time
- •Installing a Translation on an Existing Site
- •Right-to-Left Language Support
- •Language Negotiation
- •Default
- •User-Preferred Language
- •The Global $language Object
- •Path Prefix Only
- •Path Prefix with Language Fallback
- •URL Only
- •Content Translation
- •Introducing the Content Translation Module
- •Multilingual Support
- •Multilingual Support with Translation
- •Localizationand Translation-Related Files
- •Additional Resources
- •Summary
- •What Is XML-RPC?
- •Prerequisites for XML-RPC
- •XML-RPC Clients
- •XML-RPC Client Example: Getting the Time
- •XML-RPC Client Example: Getting the Name of a State
- •Handling XML-RPC Client Errors
- •Network Errors
- •HTTP Errors
- •Call Syntax Errors
- •A Simple XML-RPC Server
- •Mapping Your Method with hook_xmlrpc()
- •Automatic Parameter Type Validation with hook_xmlrpc()
- •Built-In XML-RPC Methods
- •system.listMethods
- •system.methodSignature
- •system.methodHelp
- •system.getCapabilities
- •system.multiCall
- •Summary
- •Writing Secure Code
- •Handling User Input
- •Thinking About Data Types
- •Plain Text
- •HTML Text
- •Rich Text
- •Using check_plain() and t() to Sanitize Output
- •Using filter_xss() to Prevent Cross-Site Scripting Attacks
- •Using filter_xss_admin()
- •Handling URLs Securely
- •Making Queries Secure with db_query()
- •Keeping Private Data Private with hook_query_alter()
- •Dynamic Queries
- •Permissions and Page Callbacks
- •Cross-Site Request Forgeries (CSRF)
- •File Security
- •File Permissions
- •Protected Files
- •File Uploads
- •Filenames and Paths
- •Encoding Mail Headers
- •Files for Production Environments
- •SSL Support
- •Stand-Alone PHP
- •AJAX Security, a.k.a. Request Replay Attack
- •Form API Security
- •Protecting the Superuser Account
- •Summary
- •Development Best Practices
- •Coding Standards
- •Line Indention and Whitespace
- •Operators
- •Casting
- •Control Structures
- •Function Calls
- •Function Declarations
- •Function Names
- •Class Constructor Calls
- •Arrays
- •Quotes
- •String Concatenators
- •Comments
- •Documentation Examples
- •Documenting Constants
- •Documenting Functions
- •Documenting Hook Implementations
- •Including Code
- •PHP Code Tags
- •Semicolons
- •Example URLs
- •Naming Conventions
- •Checking Your Coding Style with Coder Module
- •Finding Your Way Around Code with grep
- •Summary
- •Optimizing Drupal
- •Caching Is the Key to Drupal Performance
- •Optimizing PHP
- •Setting PHP Opcode Cache File to /dev/zero
- •PHP Process Pool Settings
- •Tuning Apache
- •mod_expires
- •Moving Directives from .htaccess to httpd.conf
- •MPM Prefork vs. Apache MPM Worker
- •Balancing the Apache Pool Size
- •Decreasing Apache Timeout
- •Disabling Unused Apache Modules
- •Using Nginx Instead of Apache
- •Using Pressflow
- •Varnish
- •Normalizing incoming requests for better Varnish hits
- •Varnish: finding extraneous cookies
- •Boost
- •Boost vs. Varnish
- •Linux System Tuning for High Traffic Servers
- •Using Fast File Systems
- •Dedicated Servers vs. Virtual Servers
- •Avoiding Calling External Web Services
- •Decreasing Server Timeouts
- •Database Optimization
- •Enabling MySQL’s Query Cache
- •MySQL InnoDB Performance on Windows
- •Drupal Performance
- •Eliminating 404 Errors
- •Disabling Modules You’re Not Using
- •Drupal-Specific Optimizations
- •Page Caching
- •Bandwidth Optimization
- •Pruning the Sessions Table
- •Managing the Traffic of Authenticated Users
- •Logging to the Database
- •Logging to Syslog
- •Running cron
- •Architectures
- •Single Server
- •Separate Database Server
- •Separate Database Server and a Web Server Cluster
- •Load Balancing
- •File Uploads and Synchronization
- •Multiple Database Servers
- •Database Replication
- •Database Partitioning
- •Finding the Bottleneck
- •Web Server Running Out of CPU
- •Web Server Running Out of RAM
- •Identifying Expensive Database Queries
- •Identifying Expensive Pages
- •Identifying Expensive Code
- •Optimizing Tables
- •Caching Queries Manually
- •Changing the Table Type from MyISAM to InnoDB
- •Summary
- •Installation Profiles
- •Creating a New Installation Profile
- •The enhanced.info File
- •The enhanced.profile File
- •The enhanced.install File
- •Using hook_install_tasks and hook_install_tasks_alter
- •Summary
- •Testing
- •Setting Up the Test Environment
- •How Tests Are Defined
- •Test Functions
- •Test Assertions
- •Summary
- •Database Table Reference
- •Resources
- •Code
- •The Drupal Source Code Repository on GIT
- •Examples
- •Drupal API Reference
- •Security Advisories
- •Updating Modules
- •Updating Themes
- •Handbooks
- •Forums
- •Mailing Lists
- •Development
- •Themes
- •Translations
- •User Groups and Interest Groups
- •Internet Relay Chat
- •North America
- •Europe
- •Asia
- •Latin America / Caribbean
- •Oceania
- •Africa
- •Videocasts
- •Weblogs
- •Conferences
- •Contribute
- •Index
- •Numbers
CHAPTER 9 ■ THE THEME SYSTEM
■ Note Any parts of your modules that output HTML or XML should be done only within theme functions so they become accessible for themers to override.
Overriding with Template Files
If you’re working with a designer, telling him or her to “just go in the code and find the themable functions to override” is out of the question. Fortunately, there’s another way to make this more accessible to designer types. You can instead map themable items to their own template files. I’ll demonstrate with our handy breadcrumb example.
Before we begin, make sure that no theme function is overriding theme_breadcrumb(). So if you created a grayscale_breadcrumb() function in your theme’s template.php file in the preceding section, comment it out. Then, create a file at sites/all/themes/grayscale/breadcrumb.tpl.php. This is the new template file for breadcrumbs. Because we wanted to change the <div> tag to a <span> tag, go ahead and populate the file with the following:
<?php if (!empty($breadcrumb)): ?>
<span class="breadcrumb"><?php print implode(' ! ', $breadcrumb) ?></span> <?php endif; ?>
That’s easy enough for a designer to edit. Now you need to let Drupal know to call this template file when looking to render its breadcrumbs. To do that, rebuild the theme registry by clearing the site’s cache files. To clear the cache, visit admin/config/development/performance and click the “Clear all caches” button. While rebuilding the theme registry, Drupal will discover your breadcrumb.tpl.php file and map the breadcrumb themable item to that template file.
Now you know how to override any themable item in Drupal in a way that will make your designers happy.
Adding and Manipulating Template Variables
In this example, we’ll look at manipulating or adding variables that are being passed into page and node templates. Let’s continue with our example of using the breadcrumb trail. First, let’s modify sites/all/themes/grayscale/breadcrumb.tpl.php to use a variable called $breadcrumb_delimiter for the breadcrumb delimiter:
<?php if (!empty($breadcrumb)): ?> <span class="breadcrumb">
<?php print implode(' '. $breadcrumb_delimiter .' ', $breadcrumb) ?> </span>
<?php endif; ?>
To set the value of $breadcrumb_delimiter, one option would be in a module. We could create sites/all/modules/crumbpicker.info:
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CHAPTER 9 ■ THE THEME SYSTEM
name = Breadcrumb Picker
description = Provide a character for the breadcrumb trail delimiter. package = Pro Drupal Development
core = 7.x
The module at sites/all/modules/crumbpicker.module would be tiny:
<?php
/**
*@file
*Provide a character for the breadcrumb trail delimiter.
*/
/**
* Implements $modulename_preprocess_$hook(). */
function crumbpicker_preprocess_breadcrumb(&$variables) { $variables['breadcrumb_delimiter'] = '/';
}
After enabling the module, your breadcrumb trail should look like Home / Administer / Site building. The preceding example illustrates a module setting a variable for a template file to use. But there
must be an easier way than creating a module every time a variable needs to be set. Sure enough, it’s template.php to the rescue. Let’s write a function to set the breadcrumb delimiter. Add the following to your theme’s template.php file:
/**
*Implements $themeenginename_preprocess_$hook().
*Variables we set here will be available to the breadcrumb template file.
*/
function grayscale_preprocess_breadcrumb(&$variables) { $variables['breadcrumb_delimiter'] = '#';
}
That’s easier than creating a module, and frankly, the module approach is usually best for existing modules to provide variables to templates; modules are not generally written solely for this purpose. Now, we have a module providing a variable and a function in template.php providing a variable. Which one will actually be used?
Actually, a whole hierarchy of preprocess functions run in a certain order, each one with the potential to overwrite variables that have been defined by previous preprocess functions. In the preceding example, the breadcrumb delimiter will be # because phptemplate_preprocess_breadcrumb() will be executed after crumbpicker_preprocess_breadcrumb(), and thus its variable assignment will override any previous variable assignment for $breadcrumb_delimiter.
For the theming of a breadcrumb trail using the Grayscale theme, the actual order of precedence (from first called to last called) would be:
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