default.conf

server {
    listen       80;
    server_name  localhost;

    # ... other default site stuff, document root, etc. ...

    location ~ ^/~(?<userdir_user>.+?)(?<userdir_uri>/.*)?$ {
        alias   /home/$userdir_user/public_html$userdir_uri;
        index   index.html index.htm index.php;
        autoindex on;

        include php5_generic;
    }
}

php5_generic

location ~ \.php$ {
    include         fastcgi_params;
    fastcgi_param   SCRIPT_FILENAME     $request_filename;
    fastcgi_pass    unix:/var/run/php5-fpm.sock;
}