Download codeigniter :

All everyone can download codeigniter on this link “https://ellislab.com/codeigniter/user-guide/installation/downloads.html”

CodeIgniter is installed in four steps:

Ø Unzip the package.

Ø Upload the CodeIgniter folders and files to your server. Normally the index.php file will be at your root.

Ø Open the application/config/config.php file with a text editor and set your base URL. If you intend to use encryption or sessions, set your encryption key.

Ø If you intend to use a database, open the application/config/database.php file with a text editor and set your database settings.

If you wish to increase security by hiding the location of your CodeIgniter files you can rename the system and application folders to something more private. If you do rename them, you must open your main index.php file and set the $system_folder and $application_folder variables at the top of the file with the new name you've chosen.

For the best security, both the system and any application folders should be placed above web root so that they are not directly accessible via a browser. By default, .htaccess files are included in each folder to help prevent direct access, but it is best to remove them from public access entirely in case the web server configuration changes or doesn't abide by the .htaccess.

After moving them, open your main index.php file and set the $system_folder and $application_folder variables, preferably with a full path, e.g. '/www/MyUser/system'.

One additional measure to take in production environments is to disable PHP error reporting and any other development-only functionality. In CodeIgniter, this can be done by setting the ENVIRONMENTconstant, which is more fully described on the security page.

Upgrading From a Previous Version

Please read the upgrade notes corresponding to the version you are upgrading from.

v Upgrading from 2.1.4 to 2.2.0

v Upgrading from 2.1.3 to 2.1.4

v Upgrading from 2.1.2 to 2.1.3

v Upgrading from 2.1.1 to 2.1.2

v Upgrading from 2.1.0 to 2.1.1

v Upgrading from 2.0.3 to 2.1.0

v Upgrading from 2.0.2 to 2.0.3

v Upgrading from 2.0.1 to 2.0.2

v Upgrading from 2.0 to 2.0.1

v Upgrading from 1.7.2 to 2.0

v Upgrading from 1.7.1 to 1.7.2

v Upgrading from 1.7.0 to 1.7.1

v Upgrading from 1.6.3 to 1.7.0

v Upgrading from 1.6.2 to 1.6.3

v Upgrading from 1.6.1 to 1.6.2

v Upgrading from 1.6.0 to 1.6.1

v Upgrading from 1.5.4 to 1.6.0

v Upgrading from 1.5.3 to 1.5.4

v Upgrading from 1.5.2 to 1.5.3

v Upgrading from 1.5.0 or 1.5.1 to 1.5.2

v Upgrading from 1.4.1 to 1.5.0

v Upgrading from 1.4.0 to 1.4.1

v Upgrading from 1.3.3 to 1.4.0

v Upgrading from 1.3.2 to 1.3.3

v Upgrading from 1.3.1 to 1.3.2

v Upgrading from 1.3 to 1.3.1

v Upgrading from 1.2 to 1.3

v Upgrading from 1.1 to 1.2

v Upgrading from Beta 1.0 to Beta 1.1

The Encryption Class now requires the Mcrypt extension. If you were previously using the Encrypt Class without Mcrypt this is a breaking change, you must install the Mcrypt extension in order to upgrade. For information on installing Mcrypt please see the PHP documentation.

Before performing an update you should take your site offline by replacing the index.php file with a static one.

Step 1: Update your CodeIgniter files

Replace all files and directories in your "system" folder and replace your index.php file. If any modifications were made to your index.php they will need to be made fresh in this new one.

Note: If you have any custom developed files in these folders please make copies of them first.

Troubleshooting

If you find that no matter what you put in your URL only your default page is loading, it might be that your server does not support the PATH_INFO variable needed to serve search-engine friendly URLs. As a first step, open your application/config/config.php file and look for the URI Protocol information. It will recommend that you try a couple alternate settings. If it still doesn't work after you've tried this you'll need to force CodeIgniter to add a question mark to your URLs. To do this open your application/config/config.php file and change this:

$config['index_page'] = "index.php";

To : $config['index_page'] = "index.php?";