How to handle redirects in WordPress

gistfile1.txt

Otto:

Step 1: Just try it as is and see what happens. WordPress's canonical
redirection is pretty darned clever in some ways, and it often can
guess the right thing to serve out of the box.

Step 2: If the built in canonical redirection isn't able to detect and
redirect accordingly, then you can add your own code to discover and
handle the redirections. The way you do this is with the
redirect_canonical filter.

add_filter('redirect_canonical','my_redirects',10,2);

function my_redirects($redirect_url, $requested_url) {
 // do stuff
 return $redirect_url;
}

The function gets the $requested_url, which is what the person asked
for, and it returns the $redirect_url, which is what WordPress thinks
it should serve.

If the $redirect_url is false, then WP will not redirect and will go
to 404 instead. But if the $redirect_url is a normal URL string, then
it will issue a 301 redirect to that string. So if you change that
$redirect_url before returning it, you can make it redirect elsewhere.

So if you can write some code to do the mapping from the old URL to
the new ones, you can make a plugin that has that mapping and then
hook it in using this filter. Voila, instant 301 handling.