Yii core messages refer to static text strings in the core Yii framework code which are meant to be displayed to end-users (e.g. core exception messages, default validation error messages). Customization of these core messages is needed in two circumstances:
By default, the decimal separator in php (also in mysql) is a dot (.).
So when we work with floats in Yii (in calculations, validation, sql statements etc.), the decimal separator has to be a dot.
If we want to use for example a comma (,) as the decimal separator, that is if we want to display numbers and enable users to enter numbers with a comma before the decimals, we have to...
Because Yii intends to be integrated nicely with third-party libraries, it does not define any global functions. Everything in Yii needs to be addressed with full class name or object scopes. For example, to access the current user, we need to use Yii::app()->user; to access application parameters, we need Yii::app()->params['name']; and so on. While editors like textmate can help alleviate the problem of these lengthy typings, it is worthwhile to define global shortcut functions to some commonly used method calls. They will make the application code look cleaner.