Intro to MVC Development in PHP
Ed Finkler • http://funkatron.com • @funkatron
#tekmvc • php|tek 2009

Thee Agenda
All About MVC
Why CodeIgniter?
The CI MVC Model
CI Basics
Running CI out of the box
Making a basic web app
Making a web api
Libraries, components, logging and caching

All About MVC
http://www.flickr.com/photos/airship/118352487/

What is MVC?

What is MVC?
1979, Norwegian, Xerox Parc
Give user the impression of interacting directly with
data
Used in GUI apps first
http://short.ie/g95zua

A Diagram
Controller
View Model

The Model
\"Represent knowledge\"
The data/business functionality

The View
Visual representation of the model
The screens and widgets of app
Gets data from model & updates model

The Controller
Link between user and system
Responsible for intercepting user input
Passes user input to view via messages

Why Does
MVC Help?

Separation of concerns
Don't mix your chocolate with my peanut butter

\"Swappability\"
Avoid tight coupling

MVC is not magic fairy dust
But understanding it and using it
can make you a better developer

Variations on
MVC
http://short.ie/k2f9rk
http://www.flickr.com/photos/stevem78/2975614995/

MVP
Model-View-Presenter (Dolphin Smalltalk variant)
Presenter primarily updates model
Presenter
View Model

PAC
Presentation-Abstraction-Controller
Presentation Control Model
Presentation Control Model
Presentation Control Model
Presentation Control Model Presentation Control Model

Light vs Heavy
Where does the logic go?

Event-driven vs direct calls
Observer pattern

http://www.flickr.com/photos/alternatewords/2332580309/
Why CodeIgniter?

Why not CakePHP or Zend
Framework or Limonade or
Symfony or Solar or Kohana
or Zoop or Yii or Akelos or
PHP on Trax or Prado or
Seagull?

Because you've gotta pick
one, dammit

All of them have value*
* except Zend Framework

That being said, CI is…
Easy to understand
Simple
doesn't require advanced OOP
Doesn't force lots of conventions
Plays well with others
Quick to get up and running
Good docs and great community
Backed by invested entity (http://ellislab.com)

CodeIgniter MVC
Implementation

More of a Passive View
Pattern
Controller
View Model
http://short.ie/5o7eg4

CI application flow
Stolen from CI user guide

App components
Front controller Helper
Routing Plugin
Security Scripts
Controller View
Model Caching
Library

Front controller
index.php

Routing
http://domain.com/index.php/controller/method/param
class Search extends Controller
{
public function single($id)
{
// [...]
}
}

Security
Filtering or blocking unsafe input

Controller
The core of everything <?php
class Site extends Controller {
\"Heavy\": you could do function Site() {
parent::Controller();
everything in controller $this->load->library('session');
}
public methods are function index() {
available as actions from // mletters model is auto-loaded
$rows = $this->mletters->getMany(10);
URL $data['rows'] = $this->_prepData($rows);
$this->load->view('index', $data);
}
private methods prefixed
with “_” function _prepData($rows) {
// do some cleanup on the data…
}
?>

Model
ActiveRecord pattern available, not required
Query binding
$sql = \"SELECT * FROM some_table WHERE id = ? AND status = ? AND author = ?\";
$this->db->query($sql, array(3, 'live', 'Rick'));
Don't like the DB layer? Use something else
Zend_DB, Doctrine, DataMapper (http://bit.ly/
datamapper), IgniteRecord (http://bit.ly/igrec) …

Library
A class designed to work on related tasks

Helper
Procedural funcs, grouped by file
Mostly for views; available in controllers
/**
* Plural
*
* Takes a singular word and makes it plural
*
* @access public
* @param string
* @param bool
* @return str
*/
function plural($str, $force = FALSE)
{
// [...]
}

Plugin
Single procedural function
More extensive functionality than helper
$vals = array(
'word' => 'Random word',
'img_path' => './captcha/',
'img_url' => 'http://example.com/captcha/',
'font_path' => './system/fonts/texb.ttf',
'img_width' => '150',
'img_height' => 30,
'expiration' => 7200
);
$cap = create_captcha($vals);
echo $cap['image'];

Script
Other scripts the CI app might use

View
Build response to client
CI Views are limited
Uses plain PHP as templating lang
<?php foreach ($rows as $row): ?>
<li class=\"letter\">
<div class=\"body\">
<h3>Dear Zend,</h3>
<p><?=$row->body?></p>
</div>
<div class=\"meta\">
<div class=\"posted\">
<a href=\"<?=site_url('/site/single/'.$row->id)?>\">Posted <?=$row->posted?></a>
</div>
<div class=\"favorite\">Liked by <?=$row->favorite_count?> person(s).
<a href=\"<?=site_url('/site/favorite/'.$row->id)?>\">I like this</a>
</div>
</div>
</li>
<?php endforeach ?>

View
Optional template markup
$this->load->library('parser'); <html>
$this->parser->parse('blog_template', $data); <head>
<title>{blog_title}</title>
</head>
<body>
<h3>{blog_heading}</h3>
{blog_entries}
<h5>{title}</h5>
<p>{body}</p>
Want a heavier template lang? {/blog_entries}
Use one. </body>
</html>

Caching
Saves response to file
Serves up file contents if cache not expired

CI Basics
http://www.flickr.com/photos/canoafurada/395304306/

CI Structure
front controller
index.php points to system and
application folders
system application
base classes & app-specific classes
built-in functionality & functionality

CI Structure
default layout

CI Structure
custom layout
only index.php is under
document root

The CI Object
$this inside controllers

The loader
$this->load->{view|library|model|helper|etc}('name');

CI Out of the box

The Welcome App
Put CI on the server
Load it in the browser
Why does Welcome load?
How URLs map
Trace with Xdebug/MacGDBp

Making a web application

Population estimates DB
Get our data from Numbrary: http://short.ie/w3f6h3)
Make a new controller
Change the default route
Config DB settings
Make a model
Make a view
Make fancier views

Make a web API
http://www.flickr.com/photos/dunechaser/2429621774/

Web API for pop. est. DB
Let users query our DB via HTTP
Return results on JSON or serialized PHP

http://www.flickr.com/photos/metaphorge/515054465/
Libraries, Components,
Logging and Caching

Autoloading
Make certain libs, models, helpers, etc available
automatically

Libraries
Extending core libs
application/libraries/MY_Library.php
Replacing core libs
application/libraries/CI_Library.php
Creating your own libs
application/libraries/Library.php
Constructor: Library();

Helpers
Make your own
application/helpers/name_helper.php
Add to existing
application/helpers/MY_name_helper.php
Example: PHP lang helper

Using non-CI components
The CI Way
Examples: Simplepie, Markdown
The dirty, bad way
require() that jazz

Caching
set cache path in config
make dir writable
enable caching in controller methods

Logging
set path in config
make dir writable
manual logging: log_message(level, msg)

Error handling
CI uses it's own error handler
Can block expected behavior
Example

Questions?
http://www.flickr.com/photos/deadhorse/508559841/
@funkatron/#tekmvc
coj@funkatron.com