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PHP
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Drupal is written in PHP
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Web application scripting language
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Open source language sponsored by Zend
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PHP is actually written in C
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Easy to learn
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Great for rapid application development
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One of the more popular languages for web
applications
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How PHP Works
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PHP is run by the web server
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PHP code embedded in web pages is compiled
and interpreted when the page is requested
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Uncompiled code means portability and rapid
refactoring
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PHP is truly dynamic
– Even variable names can be dynamic
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Code can include other scripts or libraries
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Data Persistence
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Like most web applications Drupal needs to
store data
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Data is in a database (MySQL)
– Database means content changes happen in
the database rather than in code or on files
– Makes for easy portability and backup
– Access via code, or directly at command line
– SQL is a standard, popular, well understood
language
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Drupal Hierarchy
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Drupal uses dynamic includes to load code
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What happens when there are conflicts?
– Last loaded code is the one that runs
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Drupal uses this to allow developers and users
to “extend” Drupal
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Composition of Drupal
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Drupal includes a common set of files used to
“bootstrap” Drupal
– Set up database connections, provide
authentication, present output, etc.
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Drupal has additional modules
– These are dynamically included depending on
configuration
– 33 modules are included in the Drupal core
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Running Drupal
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Every Drupal request goes to index.php, even if
the URL looks like a different location
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Index.php does bootstrapping:
– checks database for enabled modules
– loads modules that are appropriate
– checks permissions
– queries database for content
– applies theme
– renders the page
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When things go bad
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When Drupal encounters a PHP fatal error:
– White screen of death
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What has happened:
– PHP hit an error that forced a stop to
compilation
– PHP logs the error in the web server logs
– Potentially Drupal logs the error in the Drupal
watchdog table
– Execution dies silently without output
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Top Level Files
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Several critical php files:
cron.php - web interface for scheduled tasks
index.php - everything flows through index.php
install.php - installation file (remove)
update.php - update install (for new modules)
xmlrpc.php - provide remote procedures (opt.)
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Various other text files
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How to install Drupal
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You need a database and a web server with
PHP already running
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Create a database for the Drupal site
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Download the Drupal code from Drupal.org
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Point web browser and Drupal root and the rest
is automated
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Modules
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Modules can be installed in a number of
locations
– /modules
– /sites/all/modules
– /sites/default/modules
– /profiles/profileName/modules
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Modules should be installed in:
– /sites/all/modules
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What is a “module”
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Modular piece of code that extends Drupal
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Uses the Drupal API
– Just a set of functions defined in the Drupal
core (or other modules)
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Provide drop in functionality
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Can be enabled/disabled (in the database)
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Provide additional functionality without altering
the Drupal core
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Look and Feel
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Drupal takes a similar approach to display
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Display is a separate area of Drupal
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Many components of Drupal are defined in the
“theme”
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Themes are comprised of HTML, CSS, PHP
and imagery
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Themes utilize the same hierarchy as modules
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Theme files are called “templates”
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Advantage of Themes
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Themes follow a convention (standardization)
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Can easily be swapped out to quickly change or
upgrade the look of a site
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Useful because theme developers need not
necessarily be Drupal developers (or PHP
programmers)
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Can provide powerful filters to screen output in
Drupal
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Blocks
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Blocks are pieces of content placed in regions
of Drupal pages
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Blocks are arbitrary pieces of content
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Usually the stuff that appears in sidebar, header
and footer content
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Blocks can be content, forms, special lists,
polls, or arbitrary HTML
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Themes define regions for blocks
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Nodes
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Drupal organizes most content around the
concept of a “node”
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Nodes are just pieces of content
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Only a few things aren't nodes – users, groups,
modules, and themes being the main ones
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Other stuff, from calendar events, to RSS feed
items, to page content is a node
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How Nodes Work
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Nodes support versioning
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As a result node content is stored in the
node_revisions table
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The Drupal “node” table only stores metadata
about nodes
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Nodes can have various modules applied to
them to adjust input and output handling
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Organizing Nodes
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There are all sorts of nodes, how do we keep them
organized?
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Drupal supports a categorization of nodes that allows for
various node “definitions”
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Content types allow Drupal users to define various fields
for different types of nodes
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For instance, one node might include a URL, another a
title
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Using “fields” specific to node types allows sorting and
display (rather than having the data stuck in a node
“body”)
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Content Types
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“Page” and “Story” are two default content
types
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The titles are arbitrary
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Content types define input fields and how the
content is displayed
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New content types can easily be created
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Content type creation should follow careful
consideration of site architecture and purpose
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Taxonomy
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Taxonomy is another way to organize content
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Taxonomy are “tags” that are applied to content
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“Vocabularies” set up as taxonomies
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Vocabularies then contain terms
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Taxonomies can be extended and used for
various rules in the Drupal back end
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Taxonomy can also be used for display
purposes
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Permissions
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Drupal utilizes a Role Based Access Control
(RBAC) system
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Users are assigned to roles, roles receive
permissions
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Permissions are set through the Drupal
administrative interface
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Uid 1 user (created during install) has all
permissions
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When in doubt: it's a permissions issue
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Got Drupal, now what?
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Drupal out of the box doesn't look like much
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Drupal is extremely flexible but requires a lot of
configuration
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Changing Drupal after deployment is a pain, so
you must plan carefully
●
Drupal is a framework that doesn't make
assumptions about use cases
●
Drupal requires lots of tweaks to enable
functionality the way you want it
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