hox to fix encoding probem when extract CSV file


I want to extract CSV file with yii I did that successfuly

this is my code:

header("Content-type: Binary/CSV" );

header('Content-Disposition: attachment; filename="Facture achats' . date('YmdHi') .'.csv"');	

header("Content-Description: fichier binaire" );

header("Content-Transfer-Encoding: binary" );


echo $outputdata;

but when I open file CSV I get this : N° Facture,Date Facture,Désignation

some letters was changed.

I know the problem is the encoding but how to fix it?