set the upload_tmp_dir but file no where to be found

Solution:

PHP will delete uploaded files when the script exits, unless you’ve moved/copied the file somewhere else yourself. The upload process isn’t a “do it now and come back later to deal with it” system. It’s “deal with it now, or it’s gone”.

To retrieve the file’s temporary storage location/name, you use $_FILES['namegiveninform']['tmp_name'], and generally would use move_uploaded_file() to move the file into its permanent storage location.