"This function checks to ensure that the file designated by from is a valid upload file (meaning that it was uploaded via PHP's HTTP POST upload mechanism). If the file is valid, it will be moved to the filename given by to."
Laten we het eens anders zeggen.
Je kent de filename
Je kent de directory waarde upload moet komen.
Hoe moet het dan gaan in de praktijk want dit werkt niet
move_uploaded_file($file, $target_dir);