I don't know what to call this

[psycorpse]

I am reviewing some php nuke code and I am wondering how they are getting some text. Here is what my question is?

in this fake code..
"You are"._SOMETEXT."!";

What is the _SOMETEXT and how do you use it?
If there is somewhere that I can read up on this that would be great but I dont have a clue of what it is called. Any help would be great.

Thanks in advance.

[onion2k]

Its a constant. Its created using define("_SOMETEXT","This is what goes in everything we want some text"); ... its exactly the same as a variable, only it can't be changed by mistake, and its a little quicker as its replaced during the preprocessing stage of compilation.