How to correctly test if the url is under HTTPS with PHP

Most likely your application will be under a load balancer when in production. If you need to test if the url is HTTPS with PHP you will probably use env('HTTPS'), but under a load balancer that wont work.

You will need to check for HTTPXFORWARDED_PROTO server variable.

Off course testing this under your local environment can be painful, but here is a small tip that works wonders. Change your http-ssl.conf and on your virtual host add:

RequestHeader set X-Forwarded-Proto "https"

This will automatically add the HTTPXFORWARDED_PROTO on the response header from Apache to your app.

The same logic can be used for other Apache header responses.