Hi,
for which part of this task do you need help?
The following command prints a file to the user:
http://php.net/manual/en/function.file-get-contents.php
eg:
echo file_get_contents("myfile.csv");
edit
Try to add the following headers to your php-page, which will be called for your ajax call:
header("Content-Type: text/csv");
header("Content-Disposition: attachment; filename=\"export.csv\"");
henchman
2010-03-04 20:37:51