nginx with php-fpm downloading php files rather than executing them on mac os x (local environment)

Instead of specifying the PHP section in the nginx.conf file, can you specify a server location in the default file (within sites-available directory) and either reload or restart nginx:

server { 
        listen 80;
        listen [::]:820; #ipv6only=on;
        root /var/www/;  ##assuming your PHP application is in /var/www/
        index index.php index.html index.htm;
        server_name PHPApp;

        location ~ \.php$ {
                fastcgi_split_path_info ^(.+\.php)(/.+)$;
                fastcgi_pass unix:/var/run/php5-fpm.sock;
                fastcgi_index index.php;
                include fastcgi_params;
        }
}

Also, make sure that your nginx.conf file has the following directive:

include /etc/nginx/sites-enabled/*;