I am using the following code to stream a pdf to the browser:
header(\"Cache-Control: must-revalidate, post-check=0, pre-check=0\"); header(\"Pragma: public
That behavior is controlled by the browser settings, so I don't think theres a way to force the "Save as" dialog to be opened.
You could try not specifying a name for the file, but I do think that it will just inherit the scripts name instead.