How to fix Apache Content-Type for PHP-parsed CSS?

I set up my Apache 2 server to parse CSS files in a specific virtual host with PHP:

AddType application/x-httpd-php .css

However, the text is served with the wrong headers, meaning that the CSS files aren't used, at least in Firefox. Setting Content-Type: text/css with PHP fixes the problem, but I don't want to do that for every CSS file. How to fix this?

I think the best way to do this is to add this to the virtual host:

AddHandler application/x-httpd-php .css

In case this results in a wrong mime-type add this too:

<Files *.css>
  Header set Content-type "text/css"
</Files>

In case you want this to only apply to css files in a specific directory you can add it to a .htaccess file in that directory instead of the virtual host or add a Directory-directive for that directory to the virtual host i.e.

<Directory /foo>
  AddHandler application/x-httpd-php .css
  <Files *.css>
    Header set Content-type "text/css"
  </Files>
</Directory>