My Following code is working fine when I set
$target = \"size_images/14_20131216231522_cashew.jpg\";
But Not Working
You are misunderstanding how move-uploaded-file() works. It is similar to "File Save", namely you have to tell the PHP script a locally-writeable directory and file name where the file goes.
You mention you're trying to go from "subdomain" to "main domain"... if these two web urls are hosted on the same machine, this will be possible, you will just choose the directory that has the files for the "main domain" site.