Upgrading from 1.7.2 to 2.0.0
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 except your application folder.
Note: If you have any custom developed files in these folders please make copies of them first.
Step 2: Adjust get_dir_file_info() where necessary
Version 2.0.0 brings a non-backwards compatible change to get_dir_file_info() in the File Helper. Non-backwards compatible changes are extremely rare in CodeIgniter, but this one we feel was warranted due to how easy it was to create serious server performance issues. If you need recursiveness where you are using this helper function, change such instances, setting the second parameter, $top_level_only to FALSE:
get_dir_file_info('/path/to/directory', FALSE);
Step 3: Convert your Plugins to Helpers
2.0.0 gets rid of the "Plugin" system as their functionality was identical to Helpers, but non-extensible. You will need to rename your plugin files from filename_pi.php to filename_helper.php, move them to your helpers folder, and change all instances of:
$this->load->plugin('foo');
to
$this->load->helper('foo');
Step 4: Update stored encrypted data
Note: If your application does not use the Encryption library, does not store Encrypted data permanently, or is on an environment that does not support Mcrypt, you may skip this step.
The Encryption library has had a number of improvements, some for encryption strength and some for performance, that has an unavoidable consequence of making it no longer possible to decode encrypted data produced by the original version of this library. To help with the transition, a new method has been added, encode_from_legacy() that will decode the data with the original algorithm and return a re-encoded string using the improved methods. This will enable you to easily replace stale encrypted data with fresh in your applications, either on the fly or en masse.
Please read how to use this method in the Encryption library documentation.
Step 5: Remove loading calls for the compatibility helper.
The compatibility helper has been removed from the CodeIgniter core. All methods in it should be natively available in supported PHP versions.
Step 6: Update Class extension
All core classes are now prefixed with CI_. Update Models and Controllers to extend CI_Model and CI_Controller, respectively.
Step 7: Update Parent Constructor calls
All native CodeIgniter classes now use the PHP 5 __construct() convention. Please update extended libraries to call parent::__construct().
Step 8: Update your user guide
Please replace your local copy of the user guide with the new version, including the image files.