mod_rewrite: environment variables aren't being expanded in RewriteConds

Question

I've got a RewriteCond in a .htaccess similar to:

RewriteCond "%{ENV:FOO}" =bar

But the ${ENV:FOO} is being expanded to the value of FOO, it's always blank.

For example, if I SetEnv FOO "bar" just before the RewriteCond, then crank up the RewriteLogLevel, I get this in my rewrite log:

RewriteCond: input='' pattern='=bar' => not-matched

What am I doing wrong here? How can I make environment variables expand inside of RewriteConds?

Also, if I add a silly RewriteRule like RewriteRule .* %{ENV:FOO}, I can see in the rewrite log that the variable is being correctly expanded there.

My Apache version is 2.2.17.

Edit: I've found another reference to this problem. It seems like a “solution” is to use SetEnvIf instead of SetEnv… =\

Additionally, it doesn't seem like the location of the SetEnv has any effect. I've put it both in httpd.conf and in the .htaccess, and neither work.

Answer 1

Ah, here we go. From the SetEnv documentation (under "caveats"):

The SetEnv directive runs late during request processing meaning that directives such as SetEnvIf and RewriteCond will not see the variables set with it.

So, for now, I guess I'm using:

SetEnvIf _ .* FOO=bar