Boolean (or Keyword) Search in Yii


I have a search form with some search fields to search the database. I have successfully implemented the search functionality for all the fields except for the keyword search. I intend to have a keyword search with Boolean search capability.

Can someone please give me a detailed step by step guide on how to implement a keyword search functionality in yii.

NB: I have a text area where users are meant to type in search keywords. The code will search through some columns and return rows that have the keywords. Boolean operators like +, "", NOT should be usable with the keywords.