CodeIgniter – Application Architecture

Application Architecture

The architecture of CodeIgniter application is shown below.

Figure: CodeIgniter Application Flowchart

· As  shown  in  the  figure,  whenever  a  request  comes  to  CodeIgniter,  it  will  first  go to index.php page.

·In the second step, Routing will decide whether to pass this request to step-3 for caching or to pass this request to step-4 for security check.

·If  the  requested  page  is  already  in  Caching,  then  Routing  will  pass  the  request to step-3 and the response will go back to the user.

·If  the  requested  page  does  not  exist  in  Caching,  then  Routing  will  pass  the requested page to step-4 for Security checks.

·Before   passing   the   request   to   Application   Controller,   the   Security   of   the submitted data is checked. After the Security  check, the Application Controller loads  necessary  Models,  Libraries,  Helpers,  Plugins  and  Scripts  and  pass  it on to View.

·The  View  will  render  the  page  with  available  data  and  pass  it  on  for  Caching.  As the   requested   page   was   not   cached   before   so   this   time   it   will   be   cached   in Caching, to process this page quickly for future requests.

Directory Structure  

The image given below shows the directory structure of the CodeIgniter.

Figure: Directory Structure

CodeIgniter directory structure is divided into 3 folders:

·Application

·System

·User_guide

Application

As the name indicates the Application folder contains all the code of your application that you  are  building.  This  is  the  folder  where  you  will  develop  your  project.  The  Application folder contains several other folders, which are explained below:

·Cache:   This   folder   contains   all   the   cached   pages   of   your   application.   These cached pages will increase the overall speed of accessing the pages.

·Config:  This  folder  contains  various  files  to  configure  the  application.  With  the help  of  config.php  file,  user  can  configure  the  application.  Using  database.php file, user can configure the database of the application.

·Controllers:  This  folder  holds  the  controllers  of  your  application.  It  is  the  basic part of your application.

·Core: This folder will contain base class of your application.

·Helpers: In this folder, you can put helper class of your application.

·Hooks:  The  files  in  this  folder  provide  a  means  to  tap  into  and  modify  the  inner workings of the framework without hacking the core files.

·Language: This folder contains language related files.

·Libraries: This folder contains files of the libraries developed for your application.

·Logs: This folder contains files related to the log of the system.

·Models: The database login will be placed in this folder.

·Third_party:  In  this  folder,  you  can  place  any  plugins,  which  will  be  used  for your application.

·Views: Application’s HTML files will be placed in this folder.

System

This  folder  contains  CodeIgniter  core  codes,  libraries,  helpers  and  other  files,  which  help make  the  coding  easy.  These  libraries  and  helpers  are  loaded  and  used  in  web  app development.

This  folder  contains  all  the  CodeIgniter  code  of  consequence,  organized  into  various folders:

·Core:  This folder contains CodeIgniter’s core class.  Do  not  modify  anything  here. All  of  your  work  will  take  place  in  the  application  folder.  Even  if  your  intent  is  to extend  the  CodeIgniter  core,  you  have  to  do  it  with  hooks,  and  hooks  live  in  the application folder.

·Database:   The   database   folder   contains   core   database   drivers   and   other database utilities.

·Fonts: The fonts folder contains font related information and utilities.

·Helpers:  The  helpers  folder  contains  standard  CodeIgniter  helpers  (such  as  date, cookie, and URL helpers).

·Language:  The  language  folder  contains  language  files.  You  can  ignore  it  for now.

·Libraries: The libraries folder contains standard CodeIgniter libraries (to help you with  e-mail,  calendars,  file  uploads,  and  more).  You  can  create  your  own  libraries or   extend   (and   even   replace)   standard   ones,   but   those   will   be   saved   in   the application/libraries   directory   to   keep   them   separate   from   the   standard CodeIgniter libraries saved in this particular folder.

User_guide

This is  your  user  guide  to  CodeIgniter.  It  is  basically,  the  offline  version  of  user  guide  on CodeIgniter  website.  Using  this,  one  can  learn  the  functions  of  various  libraries,  helpers

and  classes.  It  is  recommended  to  go  through  this  user  guide  before  building  your  first web app in CodeIgniter.

Beside  these  three  folders, there is one more important file named “index.php”. In  this file,  we  can  set  the  application  environment  and  error  level  and  we  can  define  system and  application  folder  name.  It  is  recommended,  not  to  edit  these  settings  if  you  do  not have enough knowledge about what you are going to do.