title: How to enable php in NixOs
body: <p>I'm trying to setup an LAMP environment with NixOs.
  I managed to have mysql and apache running, but I can't find a way 
  to enable php. 
  At the moment, apache is <em>serving</em> php file as text instead of executing it.</p>
  
  <p>I've seen there is a <code>enablePHP</code> option in the <code>appache-httpd/default.nix</code> file but it doesn't seem visible (it doesn't appear when I do <code>man configuration.nix</code> and I get an error message if I try to set it to true).</p>