The PDF files are OK, they do open correctly in Adobe Reader.
I read from somewhere that IE is somewhat picky about things, therefore I downloaded and installed Firefox, and voilá, the xml stuff started to work as it was supposed to. And changed the script from having been
header("Content-Type: application/octet-stream");
header("Content-Disposition: inline; filename=\"".$file_name."\"");
header("Content-Length:".filesize($full_path));
sleep(1);
readfile($full_path);
to:
$path_to_image="c:\\temp";
$file_name=$_GET['file_name'];
$full_path=$path_to_image."\\".$file_name;
$fop=fopen($full_path, 'r');
header("Cache-Control: no-cache, must-revalidate");
header("Content-Disposition: attachment; filename=".basename($file_name));
header("Content-Type: application/pdf");
header("Content-Length:".(filesize($full_path)));
sleep(1);
//readfile($full_path);
fpassthru($fop);
Although I also added, as You can see, some "header("Cache-Control: no-cache, must-revalidate");", which might have had some effect on the outcome. But anyway, now I can "import" a xml - file, and then another, and then another, etc.
About the PDF files not opening...I found that if I place the files (and make the script look for them) in a folder where the path to this folder does NOT include any spaces the images were directly viewable. I also tried to get the thing working by saving the PDF files on a remote (network) drive (NAS), which was mapped as drive Y: to the workstation. This had the same effect as a path with spaces: Only now the error message was not the one in the beginning, but rather one which mentioned the file having been encoded somewhat incorreclty.
But anyway, it works now, from a local folder, with the path not containing spaces.
The work continues, though, since I would like it to work using the NAS also. But so far, I consider this case closed.
Thank You for Your efforts.