How do I disable GZip with SetEnvIfNoCase in Apache .htaccess?

I want to disable GZip for certain pages. I have this in my .htaccess, but it still turns GZip on (Content-Encoding: gzip) when visiting dashboard/index.

<ifmodule mod_deflate.c>
  AddOutputFilterByType DEFLATE text/text text/html text/plain text/xml text/css application/x-javascript application/javascript
  BrowserMatch ^Mozilla/4 gzip-only-text/html
  BrowserMatch ^Mozilla/4\.0[678] no-gzip
  BrowserMatch \bMSIE !no-gzip !gzip-only-text/html
  SetEnvIfNoCase Request_URI /dashboard/index no-gzip dont-vary

I tried to add Header set MyHeader %{REQUEST_URI} to see what the Request_URI was, but it gave an Internal Server Error.

I also tried the regex dashboard/index, dashboard/index.*, "/dashboard/index", etc., and tried SetEnvIfNoCase REQUEST_URI ..., but GZip was still on.

If I comment #AddOutputFilterByType, then GZip is turned off.

I'm using Apache 2.4.16, Yii 2.0.7, PHP. I'm using FPM in production, so apache_setenv() is not available.

Solution

You're probably using rewrites to get rid of index.php in the URL. Due to the stage at which SetEnvIf runs during the request, index.php will be part of the Request_URI var used (which is distinct from %{REQUEST_URI}).

It's nowadays quite common to not use PATH_INFO for rewrites, but just plainly rewrite to index.php, where code just reads the original REQUEST_URI info. In that case, Request_URI in SetEnvIf will be just "index.php", so you'd need to set a flag env var in a special dummy rewrite for that URL, and reference it later with a REDIRECT_ prefix (as there is an internal redirect stage on rewrites where mod_rewrite prefixes all existing env vars with REDIRECT_):

RewriteRule ^dashboard/index - [E=no-gzip:1]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule . index.php [L]
SetEnvIf REDIRECT_no-gzip 1 no-gzip

There is a slightly less verbose way if you rewrite to PATH_INFO (so "/foobar" turns to "/index.php/foobar" using e.g. a RewriteRule (.*) index.php/$1 rule):

RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule (.*) index.php/$1 [L]
SetEnvIfNoCase REQUEST_URI ^/index.php/dashboard/index.*$ no-gzip dont-vary

But that seems more brittle since it'll break if you change the RewriteRule mechanics.