PHP on Shared Server

Hello - We are installing PHP on a shared Linux webserver. We are *NOT* using it as a module (for reasons which I won't go into). Anyhow, my question is regarding the following directive: upload_tmp_dir Since we are not using it as a module, we cannot define this variable inside the virtual user setting in Apache (or can we?). If this directive is not defined, where do the files go temporarily? (/tmp?) I guess I just don't understand the tmp_dir issue. If I have a script for file uploads, the files should go wherever it is stated in the script...Under what circumstances is the tmp_dir used? Bottom line - We arent using it as a module, we want to give customers ability to upload files (shared enviroment), but we don't want the risk of filling up system directories (e.g. /tmp). Ideas? Thanks! Steve