Форуми / Cotonti / Support / Tags and url Rewrite Problem

What rewrite rules do you use for it?

That will likely work, but it's a hack. Next time you upgrade Cotonti you'll have to make this modification again.

What you should do is:
- Open datas/urltrans.dat and add this line at the top

page	*	{page_url_structure()}

- Open/create system/functions.custom.php and add this:

function page_url_structure(&$args, &$spec)
{
    global $sed_cat, $pag, $row, $rpagecat;
 
    $page_cat = (!empty($sed_cat[$rpagecat]['path']) && empty($page_cat)) ? $sed_cat[$rpagecat]['path'] : $page_cat;
    $page_cat = (!empty($sed_cat[$pag['page_cat']]['path']) && empty($page_cat)) ? $sed_cat[$pag['page_cat']]['path'] : $page_cat;
    $page_cat = (!empty($sed_cat[$row['page_cat']]['path']) && empty($page_cat)) ? $sed_cat[$row['page_cat']]['path'] : $page_cat;
    $url =  str_replace('.', '/', $page_cat).'/';    
    if($args['id'])
    {
        $url .= $args['id'];
        unset($args['id']);
    }
    else
    {
        $url .= urlencode($args['al']);
        unset($args['al']);
    }
    return $url;
}

- Then open .htaccess and add this:

RewriteEngine On
#for page id
RewriteRule ^(articles|news)/([a-z-]+)/([a-z-]+)/([a0-9]+)$ page.php?id=$4 [QSA,NC,NE,L]
RewriteRule ^(articles|news)/([a-z-]+)/([0-9]+)$ page.php?id=$3 [QSA,NC,NE,L]
RewriteRule ^(articles|news)/([0-9]+)$ page.php?id=$2 [QSA,NC,NE,L]

#for page alias
RewriteRule ^(articles|news)/([a-z-]+)/([a-z-]+)/([a-zA-Z0-9-_]+)$ page.php?al=$4 [QSA,NC,NE,L]
RewriteRule ^(articles|news)/([a-z-]+)/([a-zA-Z0-9-_]+)$ page.php?al=$3 [QSA,NC,NE,L]
RewriteRule ^(articles|news)/([a-zA-Z0-9-_]+)$ page.php?al=$2 [QSA,NC,NE,L]

header("Location: ".sed_url(...)) is bad practice and should be replaced with sed_redirect(sed_url(...))

Yes, I know. sed_redirect is actually the same as header Location, but it allows for a fallback to <meta refresh> in case header Location is unsupported for some reason.
In the core (and plugins), all URLs should be created using sed_url(), since this allows for the automated rewriting with urltrans.dat. Absolute URLs may prevent this from working correctly with dynamic subdomains (since it prepends the base domain as set in the configuration panel, which usually contains www as subdomain).