Is $_SERVER['REQUEST_SCHEME'] reliable?

The REQUEST_SCHEME environment variable is documented on the Apache mod_rewrite page. However, it didn't become available until Apache 2.4.

I only have Apache 2.2 so I created an environment variable. I added the following to the top of my .htaccess file.

RewriteEngine on

# Set REQUEST_SCHEME (standard environment variable in Apache 2.4)
RewriteCond %{HTTPS} off
RewriteRule .* - [E=REQUEST_SCHEME:http]

RewriteCond %{HTTPS} on
RewriteRule .* - [E=REQUEST_SCHEME:https]

Now I can use

• %{ENV:REQUEST_SCHEME} in other rewrite conditions and rules
• $_SERVER['REQUEST_SCHEME'] in my PHP code

I don't have to do extra messy conditional checks everywhere, and my PHP code is forward compatible. When Apache is upgraded, I can change my .htaccess file.

I don't know how you'd apply this to a Windows environment. This is probably not a good solution for distributed code, but it works well for my needs.

It is hard to prove that it is reliable, but it is easy to prove that it is not reliable (if only I could provide a case which it does not work). And I can prove that it is unreliable because it does not work with IIS 7.0 + PHP 5.3