いろいろ試してググッた結果の備忘録!!!
.htaccessに追記
RewriteEngine On
RewriteCond %{http_host} ^www.oldtest.com
RewriteRule ^(.*) http://www.newtest.com/$1 [R=301,L]

■.htaccess
Mod-Rewriteをサポートしていない
Redirect 301 / http://www.newtest.com/

■php
header( “HTTP/1.1 301 Moved Permanently” );
header( “Location: http://www.newtest.com/test.html” );