I found it very annoying that php data to excel is not so straight forward as one might think ,lots of wrong stuff here.
The thing is, as a developer you don't know a lot about encoding.
So you don't really think about it until you have bugs, than you start searching for a better solution, I found this.
Meaning you manually convert encoding to support excel, and add BOM.
Just wanted to gather a few links together for future use.