It seems that a simple download of a PHP generated CSV file (with a vnd.ms-excel mime type for the sake of opening it with (Open)Office readly upon the "Save as..." dialog, when present) always gets the unwanted .xls extension when the UA is Google Chrome. The file would then be named as myfile.csv.xls. Firefox behaves correctly. I wonder if it is a bug, a feature or a misunderstanding of some references. Thank you.