[fw-mvc] Creating Zip Files

Hello,

I am trying to create a zip file so I can download multiple .pdf files. The problem I am having is that when I create the Zip file, I do not know where it gets created, and the files are never written to it.
I am using the pretty standard code :

if ($zip->open($archive_file_name, ZIPARCHIVE::CREATE )!==TRUE) {
exit("cannot open <$archive_file_name>\n");
}

to create the file, but I am unable to set the file path because I do not know where the zip file is located. Does anyone know where the file is created so I can write the files to it and download a zip file with something in it?

Regards,
Thomas