问题
I want to conditionally set cache headers depending on what path files are accessed from. Basically, accessing http://www.example.com/cache/$cache_key/* should serve files with far in the future cache headers.
I'm using a rewrite rule to set an environment variable and then attempting to set cache control headers based on that variable. However, it seems like the variable is being set too late in the process or something; the conditional header rules are never getting executed.
RewriteRule ^cache/.*?/(.*) /$1 [env=asset:true,L]
Header set Cache-control "max-age=30"
Header set Cache-Control "max-age=31536000" env=asset
Header unset ETag env=asset
Is there a better way to do this? I've tried a couple of combinations of Directory and Location blocks with no success.
回答1:
Using phpinfo() I determined the environment variable ends up not being set at all on the rewritten request, so the problem isn't the order of the request, it's that it seems to toss the variable out. Using the query string instead of the URL and not rewriting seemed to be the only way I could get this working. I do agree, it seems like there should be a better way.
RewriteCond %{QUERY_STRING} longcache=true(&|$)
RewriteRule .* - [ENV=LONGCACHE:true,L]
Header set Cache-Control "max-age=30" env=!LONGCACHE
Header set Cache-Control "max-age=31536000" env=LONGCACHE
MORE DIFFERENT ANSWER OBTAINED BY OPENING EYES:
Your asset environment variable gets renamed to REDIRECT_asset after the redirect, so your conditional Header directive needs to be:
Header set Cache-Control "max-age=31536000" env=REDIRECT_asset
来源：https://stackoverflow.com/questions/7812407/conditionally-setting-cache-headers-in-apache