7 reasons why Yii framework is better than CodeIgniter

1. Gii code generator. Gii can create template models, views, controllers and forms. The special case CRUD really makes it stand out. You simply give it the database table name, and it creates model with all the attributes. You just define data type (numeric, etc.) whether field is required, and those rules get applied ALWAYS when you try to save/update the data. In CodeIgniter, you need to validate it on each action. The difference is that CodeIgniter is form-oriented while Yii is data-oriented
2. Form handling. Gii generated forms use “active” fields. This means that when some field is not validated, yii would display the same form to fix the problem with all the data filled in
3. HTML Grid component. Enables to display data in tabular way with automatic sorting, paging, coloring of even and odd rows, etc.
4. jQuery integration. This means that stuff like date-picker or auto-complete input boxes are usually one line of PHP code and Yii spits out all the required Javascript, HTML and CSS code.
5. Translations. Creating multilingual websites in Yii is really easy. With CodeIgniter you would have to create your own way of doing it.
6. Database relations. Yii supports lazy loading. This means that you don’t have to write JOINs each time you need to get a value of related table (for example: name of author of a blog post). If you have a ActiveRecord instance of blog post as $post, you simply refer to author’s name like this: $post->author->name. Yii would execute the needed SQL to get it.
7. Consistency. Yii is much better choice if you have multiple developers working on the project. Yii introduces rules how stuff should be done, and there is no reinventing the whell. This means that all developers create the code that others can pick up easily.