Configure Server to Force Using HTTPS for phpFox Site

Cloudfare

In case you are using Cloudflare service, follow Cloudfare support to force
your site to https
https://support.cloudflare.com/hc/en-us/articles/200170536-How-do-I-redirect-all-visitors-to-HTTPS-SSL

HTACCESS

Make sure to replace example.com with the domain name you're trying force to https

    RewriteEngine On 
    RewriteCond %{HTTP_HOST} ^example\.com [NC]
    RewriteCond %{SERVER_PORT} 80 
    RewriteRule ^(.*)$ https://www.example.com/$1 [R,L]

NGINX

On server config section add following lines

   rewrite     ^   https://$server_name$request_uri? permanent;

example

server {
    listen      80;
    server_name signup.mysite.com;
    rewrite     ^   https://$server_name$request_uri? permanent;
}