Environment Variables

[Shawazi]

I've been working with PHP for years and am aware you can set envi variables and call them later by just using MYVAR in nice capital letters with no dollar sign. My question is, what's the special purpose in these? Seems like something important I missed out on with all the self-teaching.

[Weedpacket]

Those aren't environment variables, those are [man]constants[/man]. Look through the manual; you'll see them all over the place, and should give you a few clues as to why they're used.