Basic authentication for subsite only - .htaccess

Question

I have a single site, which I want to protect. It's /phpinfo on the website.
There are several redirects. My apache file looks like this:
RewriteEngine On
... A list of RewriteRules
RewriteRule ^(phpinfo)$ index.php?controller=$1
index.php takes controller as an argument and includes the specific site that is viewed.
I use basic authentication like this on several places already, which works fine:
AuthUserFile /var/www/....../.htpasswd
AuthGroupFile /dev/null
AuthName "Protected content"
AuthType Basic
<Limit GET>
require valid-user
</Limit>
But, the question is how can I limit this basic authentication to /phpinfo on the server, so only this site is protected? Ideally the AuthUserFile points to a relative directory so I can deploy this on the live server without needing to change this path.

Answer 1

A solution using PHP and not htaccess. It's simple yet effective.
if (!isset($_SERVER['PHP_AUTH_USER']) || $_SERVER['PHP_AUTH_USER'] != Config::AdminUser || $_SERVER['PHP_AUTH_PW'] != Config::AdminPassword)
{
header('WWW-Authenticate: Basic realm="Protected content"');
header('HTTP/1.0 401 Unauthorized');
die('Protected content');
}