To answer your question, these should work as long as:
- Your HTTP server passes these values along to PHP (I don't know any that don't)
- You're not accessing the script via command line (CLI)
But, if I remember correctly, these values can be faked to an extent, so it's best not to rely on them.
My personal preference is to set the domain name as an environment variable in the apache2 virtual host:
# Virtual host
setEnv DOMAIN_NAME example.com
And read it in PHP:
// PHP
echo getenv(DOMAIN_NAME);
This, however, isn't applicable in all circumstances.
