Try to use the below code which will return value to your call to see if it returns true or false.
PHP Code:
rename($subdomain."/pictures/upload/".$backup_file_name, "/Volumes/my_usb_hd/".$backup_file_name)
or die('rename failed!');
If it doesn't work then in that case you need to check out which version of PHP are you using it, if you are using older version of PHP 4.3, then this might be one of the reason and at it might also happen that on your system PHP doesn't have any permission to write the external hard drive have a check for the same.
Bookmarks