Problem In Setting Up Aptana Studio 3 With Yii

I want to use aptana studio 3 for Yii development due to its default black theme. I am using ubuntu 12.04 and installed Aptana. I have added Yii framework directory in Library, But code completion is not working. When i type Yii::app()-> nothing pops up, but when i do same in netbeans, it works fine. Netbeans Fonts and theme appear very poor in ubuntu. have anyone setup Aptana for Yii with code hints? kindly advise.