Please enable HSTS to avoid sslstrip or a MITM replacing the http page.
https://en.wikipedia.org/wiki/HTTP_Strict_Transport_Security

With PHP check if the page is been served in HTTP, if so redirect to HTTPS.
In HTTPS set the HSTS header:
(Example implementation in PHP).

That tells the browser to only use the HTTPS versión of blockchain.info for a year (31536000 seconds).
So, my browser will go directly to https even if I have no internet conection.

Thanks.