Why does my php HOME environment variable not match the HOME variable in my linux bash shell?

If I echo out HOME in the command line I get

/root

If I echo out

getenv('HOME') 

in php I get

/var/www

This messes up my AWS (amazon web services) scripts because I have a configuration file placed in my /root home directory which contains my credentials. I can can try a different way of loading my credentials but I want to know why this is happening.