301 Permanent Redirect

301 Permanent Redirect is used in several cases: when changing the domain, when transferring the site page, to glue the site name with www and without it. This is important for passing on Page Rank (PR) and retaining search traffic.

301 redirects are the best way to maintain your position in search engines when you migrate a page or site. Code "301" is interpreted as "moved permanently".

• Simple redirect (in .htaccess file or httpd.conf for Apache):

  Redirect 301 / http://www.you.com/new.htm
  where:
  

  Redirect 301 is an instruction saying that the page has been moved
  / - means that everything from the top level of the site, including all subdirectories, will be redirected
  http://www.you.com/new.htm - new page or site (do not forget to put the last "/" if the redirect goes to the site).

  To redirect only a page, keeping the PR of the old page:

  Redirect 301 /old/old.htm http://www.you.com/new.htm
  where:
  /old/old.htm - path and name of the old page
  

  Similar syntax for site redirect:
  Redirect Permanent / http://www.you.com/

  Directory redirect example:
  RedirectPermanent /old-directory http://www.domain.com/new-directory/
  

  For example, we will redirect those who entered test to www.test.com, the rest to enter.test.com (the order of the entries is important):

  Redirect permanent /test http://www.test.com/
  Redirect permanent / http://enter.test.com/
  

  Note: for my purposes (changing the domain), the first version of a simple 301 redirect was enough.

• Using mod_rewrite (written in the .htaccess file):

  The classic task of merging site names with and without www is solved as follows:

  Options+FollowSymLinks
  Rewrite Engine on
  RewriteCond %{HTTP_HOST} ^yoursite\.com
  RewriteRule ^(.*)$ http://www.yoursite.com/$1 [R=permanent,L] .
  

  or alternative syntax:

  Options+FollowSymLinks
  Rewrite Engine On
  RewriteCond %{HTTP_HOST} ^domain\.com$ [NC]
  RewriteRule ^(.*)$ http://www.domain.com/$1 [R=301,L]
  

  The designation [R=301,L] means: redirect the client and send him a 301 status code (R=301) and make this rule last (L).

  Redirecting an old domain to a new one:

  Options +FollowSymLinks
  Rewrite Engine on
  RewriteRule (.*) http://www.newdomain.com/$1 [R=301,L]
  

  For example, if you want the rewrite.html file to be loaded instead of rewrite.htm, add to .htaccess:

  Rewrite Engine on
  RewriteBase /
  RewriteRule ^rewrite\.htm$ rewrite.html [R=permanent]
  

  To replace all .htm files with .html files:

  Rewrite Engine on
  RewriteBase /
  RewriteRule ^(.*)\.htm$ $1.html [R=permanent]
  

• Redirect to PHP:

  <?php
  header('HTTP/1.1 301 Moved Permanently');
  header('Location: http://www.newdomain.ru/newdir/newpage.htm');
  exit();
  ?>

  It's better to specify HTTP/1.1 as the older ones don't support shared hosting. Don't forget that before header is called, nothing should be output (e.g. echo or print). Therefore, it is better to put this code at the beginning of the php script. A more complete version of the php redirect with saving the transmitted page and call parameters:

  <?php
  $ref=$_SERVER['QUERY_STRING'];
  if ($ref) $ref='?'.$ref;
  header('HTTP/1.1 301 Moved Permanently');
  header('Location: http://newdomain.com/'.$ref);
  exit();
  ?>