Apache htaccess - modify query string with mod_rewrite

Question

I've recently changed scripting on my website, and this has resulted in a few 404 errors as some very old queries are no longer being redirected correctly.

I've been trying to create a rewrite rule to fix this, as it requires modifying the query string.

This is an example of a broken URI:

/index.php?/page/index.html/_/news/this-is-a-page-r34

If I can rewrite the query string as so, the request will succeed:

/index.php?/article.html/_/news/this-is-a-page-r34

So, with this in mind I have tried various rewrite rules in my .htaccess file, but have not been having any success. Amongst a few other variations, I have tried the following:

1st attempt

RewriteCond %{QUERY_STRING} ^(.*)page/index.html(.*)$
RewriteRule /index.php /index.php?%1article.html%2 [L]

2nd attempt

RewriteCond %{QUERY_STRING} ^/page/index.html/(.*)$
RewriteRule /index.php /index.php?/article.html/$1 [L]

3rd attempt

RewriteCond %{QUERY_STRING} ^/page/index.html(.*)$
RewriteRule . /index.php?/article.html$1 [L]

It does appear to be matching the RewriteCond, so that's something, but the output never seems to get rewritten according to the RewriteRule.

Can anybody see where I'm going wrong? I think I've got to the point where I've been looking at it for too long and have become code blind.

Answer 1

You need to use %1 (not $1) in your "2nd attempt" (as you did in your 1st attempt) and it looks like you should be almost there (see below for explanation):

RewriteCond %{QUERY_STRING} ^/page/index\.html/(.*)$
RewriteRule ^index\.php$ /index.php?/article.html/%1 [L]

If you're in .htaccess (or <Directory> section in server config) you need to also remove the slash prefix from the RewriteRule pattern. (This is part of the directory-prefix that is removed in per-directory rewrites.)

Literal dots should also be escaped in regex, otherwise they match any character.

%1 vs $1 back-reference

%1 is a back-reference to the first parenthesised sub pattern (ie. captured group) in the last matched RewriteCond directive.

Whereas $1 is a back-reference to the corresponding captured group in the RewriteRule pattern (ie. nothing in this case!).