Prova così

Codice PHP:
var_dump($_FILES);
echo 
'File exists: '.file_exists($_FILES['File1']['tmp_name']).'
'
;
echo 
'Destination directory exists '.file_exists('/websites/symlinks/demo/Uploads/Image').'
'
;
$written=file_put_contents('/websites/symlinks/demo/Uploads/Image/testfile.test''');
echo 
$written!==false?'File could be written':'File could not be written'