Redesigning a really old Website with old-fashioned permalinks

[dominator]

Hey SEO-Pros,

I'm currently redesigning a quite old website, with the following URL structure:

TLD/category/category.php?interview_id=819

The new Version will be a little more SEO-friendly:

TLD/interviews/name-of-interview/

I know I have to do a 301-Redirect for all the old URLs to the new ones in order to keep the (until now pretty good) Google Ranking. If the rankings drop after the redesign has been done, I'll surely get killed

So, Is there any easy way of creating these 301-Redirects (must be thousands of URLs...)?

Best Regards guys and thanks for your help!

[RyanKent]

Regex is the replacement language used to provide the logic for redirects. If you can establish a logical pattern for the redirects, then someone can write the Regex expression to perform the work.

For example, if you used category ids and whenever category_id=1 you wanted it to be replaced with /interviews, you can write an expression to do such.

Without seeing more information specific to your situation, I cannot comment if you can benefit from this method. In brief, try to find a pattern and articulate it. If you can say "I want to replace X with Y" then the solution will typically work.

[dominator]

Thanks Ryan, so this means to get for example interview_id=819 redirected to the correct article, I have to provide the ID also in the new URL?

TLD/category/category.php?interview_id=819

to

TLD/category/interview-name-819

Should be something like this in Regex:

RewriteRule ^category/([^/]+-)?([0-9]+)/?$ category/category.php?interview_id=$2

EDIT: After working on it the whole day I found the following solution (as I'm working with Wordpress). Maybe it is useful for anyone:

I'm using the following function now:

add_action('parse_request','oldsite_redirect',0); // 0=before (most) 'parse_request' calls
function oldsite_redirect() {
if (isset($_GET['interview_id'])) {
global $wpdb;
$sql = "SELECT post_id FROM {$wpdb->postmeta} " .
"WHERE meta_key='interview_id' AND meta_value='%s'";
$sql = $wpdb->prepare($sql,$_GET['interview_id']);
$post_id = $wpdb->get_var($sql);
if ($post_id) {
$permalink = get_permalink($post_id);
if ($permalink) {

wp_safe_redirect($permalink,301);
exit;

}
}
}
}

Solution found here: http://wordpress.stackexchange.com/questions/12824/url-rewrite-based-on-a-custom-field-value/