Web Application Development 2
Introduction
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Introduction
At the end of the module the student is expected to:
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Understand what is codeigniter / CI.
List the reasons why developers use CI.
Enumerate the skills needed in using CI.
Understand the steps in installing CI.
Understand the MVC web framework and its structure in CI.
Introduction
Learning and Development in PHP is simple. CodeIgniter – “a powerful PHP
framework with a very small footprint, built for developers who need a
simple and elegant toolkit to create full-featured web applications.” It sounds
very complex but it’s pretty straightforward.
CodeIgniter is developed by Ellislab and used by millions worldwide.
Developers prefer to use CI for its rapid application development. It has rich
and reusable libraries and class for your website’s foundation.
Instead of creating your website from native PHP scratch, why not make it
more organized and powerful using CodeIgniter.
Why use CodeIgniter or CI.
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CI is an application framework
CI is free
CI is light weight
CI is fast
CI uses Model-View-Controller architecture
CI generates Clean URLs
CI is Extensible
CI is thoroughly documented
CI has a friendly community of users
Skills needed
The following are the items you need to know before starting to play around
CI.
PHP – A good understanding of the PHP language is a must. As long as you
can perform simple instructions (e.g. variable declaration/assignments,
conditions, loops), you will nearly understand everything here since the
CodeIgniter is made up of PHP!
Course Module
HTML – Well, you do need those html elements to manipulate to. You’ll use
this for the layout design, inputs and presentation of data.
CSS – It’s good if you know Cascading Style Sheets (CSS), and even better if
you’re using external style sheets. There are more web design processors
available if you want to level-up your knowledge on styling however if you
don’t know how, still, you can learn CI.
MySQL – This means your SQL Basic queries are required. There will some
modules on this book where you need to manipulate I/O (inputs and
outputs) from your data storage or your database. Models communicate with
the database and uses your fundamental knowledge on SQL.
JavaScript – It makes the website interact with the HTML elements. If you do
not know JS, maybe learn it sometime, okay? You need these for future
developments.
CI Installation
Step 1. Visit its website on https://www.codeigniter.com/
Step 2. Find your way to the Download link and click Download.
The current version is 3.0.6
Step 3. Extract the downloaded .zip file and place it on your local server.
Make sure your Apache server is running and online then do:
Web Application Development 2
Introduction
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Step 4. If you can see this Welcome Message. Your installation was a
success!
MVC Web Framework
Before you start CI, you should know what MVC is.
MVC stands for Model-View-Controller. MVC is an architectural pattern for
Web Development that is properly structured into layers:
Course Module
Controller – This contains the Business logic (Business Logic Layer). The
controller controls the Model and View. A controller is a class that contains
methods that decides what to call, or perform and display.
When a user sends a request on a browser, the controller will determine the
process and perform tasks based on its method; it includes calling a method
returning a value from a model, displaying and passing values on a view or
showing a 404 error page.
Views – The Presentation layer. This contains designs, layouts or templates. It
is the collection of what will show up on your browser. The view is where the
user sees and interacts with.
Models – It is also referred as the Data Access Layer. The Model
communicates with your database. It comprises of methods that execute
queries using the CodeIgniter’s Active Record pattern.
CI Directory
Basically, CodeIgniter has 3 main folders: Application, System and User
Guide. You will work with your website in Application Folder. The System
folder, keep it a habit to avoid making changes to any of the files inside. It
contains the CodeIgniter’s core files which is necessary to make it run.
User_Guide contains the offline documentations you need in developing with
websites in CI.
Web Application Development 2
Introduction
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Let’s get a little familiar with the directories:
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Course Module
Cache: This directory will contain all kinds of cached files if you are
using so. However, you will may need to provide write access for the
application to this directory as codeigniter will need to create
temporary files on this folder. To know how to use caching, please
refer to CodeIgniter caching tutorial.
Config: This directory includes settings/configuration related
information like database settings, route information, constants
declaration, items to be auto loaded etc.
Controller: This directory includes all controller definitions. It can be
said as the entry point of application also, every requests triggers a
certain method of a controller.
Core : If we need to extend the functionality of any core classes like
controller, loader, router etc, then we can declare new class here
which will extend those core classes and put the implementation
inside those.
Errors: This directory includes some basic template for showing
various kind of errors like db error, php errors, 404 errors etc, which
we can change later as per our requirements.
Helpers: This directory will include all helper files.
Hooks: This directory will include all hooks declaration.
Language: This directory will include language files. By loading
different language files, we can make our application multilingual
supported.
Libraries: This directory will include all library class files that might
need to be created for our applications.
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Logs: This directory will include all application logs. TO know how to
write log for debug/error/info, please more about error handling
Migrations: This directory will include migration helpers.
Models: This directory will include all model classes used in our
application. This section can be said as the ‘data access layer’ of our
application.
Third_party : This directory will include library files, but only those,
which are imported from third-party. So, difference between the
‘third_party’ and ‘libraries’ is that, one is for self-made libraries, for
app specific, other one is for importing party libraries.
Views : This directory will include all view template files.
Activities and Exercises