Inherited CI 1.5.4: Rebuild or update?

[eluser]phpkode[/eluser]
@rubysue, Codeigniter probably has the most stable core among all the popular PHP frameworks. Most of version upgrades maintain as much backward compatibility as possible. Ability to quickly upgrade has been one of the strongest point of CI

Please consult this user guide page on how to upgrade from 1.5.4 to 2.1.4 (current stable version). Follow the required steps sequentially from old to new version

http://ellislab.com/codeigniter/user-gui...ading.html

Please be extra careful on steps to be followed on major version changes like 1.5.4 to 1.6, 1.6.3 to 1.7 and 1.7.2 to 2.0