How to add a header if the url contain any get parameter using htaccess file?

Question

I am running PHP in Apache2 server. I would like to add header("X-Robots-Tag: noindex", true); to my pages if the url contains any get parameters like https://example.com/? or https://example.com/a.php? or https://example.com/a.php?key=value . So basically, if the url contain ? charter, the header needs to be added.

Is it possible to do it using .htaccess file and how to do it? Or is there any other way to achieve this?

Ref: https://yoast.com/x-robots-tag-play/

Answer 1

like https://example.com/? or https://example.com/a.php?

The issue in these two instances are that the query string is empty , so you can't check for this using the standard QUERY_STRING server variable ("empty" and "not-exists" evaluate to the same thing, ie. empty ).

However, you can check for a literal ? (ie. query string delimiter) in the first line of the HTTP request headers, as contained in the THE_REQUEST Apache server variable.

In the case of the first example above, this will contain a string of the form:

GET /? HTTP/1.1

And for /a.php?key=value , this will be:

GET /a.php?key=value HTTP/1.1

We can use mod_rewrite to check this and set an environment variable. Then use the header directive to set the required X-Robots-Tag HTTP response header conditionally based on whether this env var is set.

For example, near the top of the root .htaccess file:

RewriteEngine On

# Check for literal "?" in URL and set QUERY_EXISTS env var 
RewriteCond %{THE_REQUEST} \s/.*\?
RewriteRule ^ - [E=QUERY_EXISTS:1]

# Set header if QUERY_EXISTS is set
header set X-Robots-Tag "noindex" env=QUERY_EXISTS

This sets the header on 2xx "OK" responses. It won't, for instance, set the header on a 404 - but 404s are not indexed anyway, so the header is redundant. However, if you specifically need to set the header on all (non-2xx) responses then use the always condition. For example:

# Use "always" to set on non-2xx responses as well
header always set ....

Note that this is also dependent on other directives you might have in your .htaccess file. For example, if you have existing mod_rewrite directives that cause the rewrite engine to "loop" then the env var will be renamed to REDIRECT_QUERY_EXISTS and you will likely need to check for this instead in the header directive.