MySQL to Excel??? how can i export data from MySQL to excel in codeIgniter?

[eluser]Unknown[/eluser]
hello everyone:
There have a table "userInfo"(two fields,"username","address") in MySQL database. I want to
export data from the userInfo table into a excel file and can download it in website(every record has its own link,click the link ,popup a dialog,we can download the content of that record),how can i do that? i am a fresh in world of codeIgniter.