Apache mod_rewrite rule order confusion

Question

I'm trying to set up a couple of simple rules that rewrite URLs from an old version of a site based on bits of the path and the query string.

First whack at it looked like this:

RewriteEngine on RewriteMap freeitems txt:/www/www.example.com/etc/freeitems_map.txt RewriteMap items txt:/www/www.example.com/etc/items_map.txt RewriteCond %{QUERY_STRING} ^sku=(\d+)$ RewriteRule ^/free_item.php$ https://www.example.com/shop/detail/${freeitems:%1}? RewriteRule ^/item.php$ https://www.example.com/shop/detail/${items:%1}? 

That seemed to work great for the /free_item.php URLs, properly subsituting in the result from the RewriteMap, but /item.php URLs returned just the first part of the redirected URL, leaving out the results from the RewriteMap lookup. If I reversed the order of the rules, the failed/working URLs reversed. As I have always understood RewriteRule syntax, if the URL path doesn't match the pattern, the rule is skipped and processing moves on to the next one. In this case, the

I finally managed to get it working by breaking it out into two blocks:

RewriteEngine on RewriteMap freeitems txt:/www/www.example.com/etc/freeitems_map.txt RewriteMap items txt:/www/www.example.com/etc/items_map.txt RewriteCond %{QUERY_STRING} ^sku=(\d+)$ RewriteRule ^/free_item.php$ https://www.example.com/shop/detail/${freeitems:%1}? RewriteCond %{QUERY_STRING} ^sku=(\d+)$ RewriteRule ^/item.php$ https://www.example.com/shop/detail/${items:%1}? 

Can anyone enlighten me as to why the first technique failed?

EDIT: As a test, I added an additional path element to the redirected URL for the second RewriteRule. When I requested a URL that should match the second rule and not the first, that path element appears as expected. Just not the result of the RewriteMap lookup.

Thanks!

-Ben

Answer 1

The reason the first technique failed, is because the RewriteCond %1 back reference on the 2nd RewriteRule does not exist. Each RewriteRule has its own set of RewriteCond and does not share RewriteCond with other RewriteRule blocks.

See: http://httpd.apache.org/docs/2.0/mod/mod_rewrite.html#InternalRuleset

I'd also suggest adding the [L] flag, as it would appear that each rule stands on its own. eg:

RewriteRule ^/free_item.php$ https://www.example.com/shop/detail/${freeitems:%1}? [L] RewriteRule ^/item.php$ https://www.example.com/shop/detail/${items:%1}? [L] 

Good luck :)