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I'm having problems with the following config on my Apache server to Rewrite some URLs.

SetEnv PATH_TO_DIR /directory

RewriteRule ^%{PATH_TO_DIR}/([a-zA-Z0-9_\-]+)/([a-zA-Z0-9_\-\.]+)/?$ /index.php?dir=$1&file=$2

ErrorDocument 404 %{PATH_TO_DIR}/index.php?dir=null&file=error

This config used to work perfectly until I used SetEnv PATH etc. I need to use this because there are lots of rules, not just those mentioned above.

Can anyone point out my mistake?

Apache returns

%{PATH_TO_DIR}/index.php?dir=null&file=error

when I try anything (www.site.com/foo/bar for instance).

Apache returns the ErrorDocument if I just try to fetch the index.

I know it's not a problem with the rewrite rules because they work when I remove the PATH_TO_DIR variable and just hard code it.

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4 Answers 4

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You can't use per-request variables, like the ones created by SetEnv, in the regex of a RewriteRule. The Regex is compiled at startup.

You can only use variables, with the proper syntax, in the substitution of a rewriterule (2nd parm)

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  • In fact, you can't use variables set with SetEnv (mod_env) anywhere in mod_rewrite since it executes too late in the request. You would need to set the environment variable with SetEnvIf (mod_setenvif) which executes much earlier.
    – MrWhite
    Commented Oct 31, 2015 at 11:40
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The problem here was ErrorDocument which doesn't interpolate server env vars...

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  • This post was flagged as low quality by the system. Can you explain more? Such as how you know this? Or what to do about it? Cheers!!
    – closetnoc
    Commented May 8, 2016 at 19:12
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    ErrorDocument configuration option, unfortunatelly, doesn't support server variables expansion. That's way the OP was seeing %{PATH_TO_DIR}/index.php?dir=null&file=error. See stackoverflow.com/questions/10939178/… Also, obviously, env variables can't be used in a RewriteRule pattern, ^%{PATH_TO_DIR} would match literally %{PATH_TO_DIR} within the requested resource.
    – tonix
    Commented May 8, 2016 at 19:16
  • Terrific! Cheers!!
    – closetnoc
    Commented May 8, 2016 at 20:15
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    ErrorDocument interpolates server env vars starting with Apache 2.4.13. From the documentation on ErrorDocument: “From 2.4.13, expression syntax can be used inside the directive to produce dynamic strings and URLs.”
    – Michael
    Commented Jan 16, 2017 at 19:25
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Should not %{PATH_TO_DIR} be %{ENV:PATH_TO_DIR}? Also, I am not certain that you can use those variables on the rule, I think they can be used only on the RewriteCond.

Give it a look here and here, specially on that phrase:

If you wish to match against the hostname, port, or query string, use a RewriteCond with the %{HTTP_HOST}, %{SERVER_PORT}, or %{QUERY_STRING} variables respectively

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    "can be used only on the RewriteCond" - Only in the RewriteCond TestString and the RewriteRule substitution (ie. not in a regex).
    – MrWhite
    Commented Oct 31, 2015 at 11:29
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To add to covener's analysis:

You can use environment variables when using rewrites, but as you mention, SetEnv doesn't retain that info (to my knowledge). I've had good success using forced variable injections in my start up scripts. For example, when calling the apachectl or httpd binaries, you can do something like:

In your shell script do (i use in case syntax, and add an option for startMaint):

MAINTENANCE=TRUE ${APACHE_ROOT}/bin/apachectl -d ${APACHE_ROOT} -f ${APACHE_CONF} -k start

RewriteCond %{ENV:MAINTENANCE} ^TRUE$
RewriteCond %{REQUEST_FILENAME} !\.(gif|jpg|png|ico)$ [NC]
RewriteCond %{REQUEST_URI} ^/(status|uri1|uri2|uri3|etc).*$ [NC]
RewriteCond %{REQUEST_URI} !^/static/siteMaintenance.html$ [NC]
RewriteRule .* /static/siteMaintenance.html${pages:%1:NULL}? [R=302,L]
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