Fixing the Apache “unable to include…” localised errors

Apache includes a nice feature that displays localised errors. This makes use of Server Side Includes (SSI).
When you use PHP and have it also parse .html documents, your localised errors are broken. In fact, because the initial error will generate new errors, it becomes a mess. You typically see this in your error log:

unable to include "include/top.html" in parsed file /usr/share/apache2/error/HTTP_NOT_FOUND.html.var
unable to include "include/bottom.html" in parsed file /usr/share/apache2/error/HTTP_NOT_FOUND.html.var

I fixed this by using a new extension .err for the error documents.
Snippet from my apache2.conf:

    AllowOverride None
    Options FollowSymlinks Includes

    AddType text/html err
    AddOutputFilter Includes err

    AddHandler type-map var
    Order allow,deny
    Allow from all
    LanguagePriority en cs de es fr it nl sv pt-br ro
    ForceLanguagePriority Prefer Fallback

Then go into /usr/share/apache2/error and rename all files to have .err.var extension (instead of .html.var):

rename 's/\.html\.var/\.err\.var/g' *

Rename the tree files in includes dir:

rename 's/\.html/\.err/g' includes/*

Finally recursively replace the strings in the type-map files too:

perl -pi -e 's/\.html/\.err/g' *

You /usr/share/apache2/error tree now looks something like this:

contact.err.var
HTTP_BAD_GATEWAY.err.var
HTTP_BAD_REQUEST.err.var
HTTP_FORBIDDEN.err.var
HTTP_GONE.err.var
HTTP_INTERNAL_SERVER_ERROR.err.var
HTTP_LENGTH_REQUIRED.err.var
HTTP_METHOD_NOT_ALLOWED.err.var
HTTP_NOT_FOUND.err.var
HTTP_NOT_IMPLEMENTED.err.var
HTTP_PRECONDITION_FAILED.err.var
HTTP_REQUEST_ENTITY_TOO_LARGE.err.var
HTTP_REQUEST_TIME_OUT.err.var
HTTP_REQUEST_URI_TOO_LARGE.err.var
HTTP_SERVICE_UNAVAILABLE.err.var
HTTP_UNAUTHORIZED.err.var
HTTP_UNSUPPORTED_MEDIA_TYPE.err.var
HTTP_VARIANT_ALSO_VARIES.err.var
include
README

Now your localised errors should be back again, and you logs will not be flooded anymore.