I have a domain, www.timeclockmtsonline that I have 301'd to www.timeclockmts-online.com using the following PHP:<?php    header( HTTP/1.1 301 Moved Permanently );     header( Location: http://www.timeclockmts-online.com ); ?>However, when I do a google search on  with www.timeclockmtsonline.com as the search term I can see a listing for that domain.  I thought I'd see nothing.  Now I am worried about being hit with a duplicate content penalty.
Why Can I See 301'd URL in Google Index
seo;web hosting;php
Is the visibility a problem for you? The old site is still indexed by search engines and any incoming links are 301'ed to the new site. Good. Status code 301 says that content moved permanently so there is, at least in this context, no duplicate content problem.There is no benefit (more harm) in trying to get the old site from the index (e.g. with the help of a disallowing robots.txt file).Google Webmastertools offer an additional way to indicate an address change in Webmastertools -> Configuration, you can select the new domain.(And even there the 301-redirection is recommended).