replace character in query string via .htaccess

Question

My client wants a query string munged (by changing % to A) on certain pages.

For example, I can remove the query string completely on the desired pages via:

RewriteCond %{QUERY_STRING} !="" 
RewriteCond %{REQUEST_URI} ^/SpecialPage(.*) 
RewriteRule ^(.*)$ /$1? [R=301,L] #remove query string

Here's what I thought should remove % on the query string and replace with A but it's not:

RewriteCond %{QUERY_STRING} ^(.*)\%(.*)$
RewriteCond %{REQUEST_URI} ^/SpecialPage(.*)
RewriteRule ^(.*)$ /$1?%1A%2  [L]

What am I doing wrong in this? I just can't quite spot it. Thanks for the expert eyes!

Answer 1

You're real close.

The problem here is that you've got a condition and the match of your rule should be together. Your backreference to the previous RewriteCond is broken because it's for the REQUEST_URI and not the QUERY_STRING like you want.

RewriteCond %{REQUEST_URI} ^/SpecialPage(.*)
RewriteRule ^(.*)$ /$1?%1A%2  [L]

Here, the %1 backreference matches the (.*) at the end of the /SpecialPage URI. The backreferences from your query string match gets lost, and that's the ones you really want. You can combine the condition to match the REQUEST_URI with the regular expression pattern in the RewriteRule:

RewriteCond %{QUERY_STRING} ^(.*)\%(.*)$
RewriteRule ^SpecialPage(.*)$ /SpecialPage$1?%1A%2  [L]

Here, the %1 and %2 backreferences correctly reference the query string and the SpecialPage condition in the URI is met by the regex pattern.