In Apache, how can I set a Response Header only if it is not already set by the CGI application?
I need a way to automatically add the Cache-Control
header to static content on my website, but I want the CGI application to be able to specify its own Cache-Control
header too.
SetEnvIf
will not work for this purpose because it only matches Request Headers.
Is there some way to conditionally / optionally set a header if it is not already set?
1) Configure Apache to append the value of empty string ( ""
) to the Cache-Control
header to ensure the header is always included in the response.
2) Configure Apache to set the Cache-Control
header only if it's still set to empty string.
<FilesMatch "\.(css|ico|flv|gif|jpeg|jpg|js|pdf|png|swf)$">
Header append Cache-Control ""
Header edit Cache-Control "^[, ]*$" "max-age=1800, public"
</FilesMatch>
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