How should I name this function?

function get_IfUnsetAlsoSet_SomeGlobalVariable() {
    if someGlobalVariable is not set {
        someGlobalVariable = somedata
    }
    return someGlobalVariable 
}

Should I give a name like this? -> getSomeGlobalVariable(开发者_JAVA百科)

How do you name these getset functions?

I guess a name like getSomeGlobalVariable() should be easy with no confusion.

Basically you do not have to give your complete logic in a method name.

As I can understand, this smells a bit like the Singleton. So you could use this name:

GlobalInstance(); or something.

Pardon me if I'm missing something here, But as per your method

function get_IfUnsetAlsoSet_SomeGlobalVariable() {
    if someGlobalVariable is not set {
        someGlobalVariable = somedata
    }
    return someGlobalVariable 
}

It just do one thing, will set 'somedata' to 'someGlobalVariable'. Personally I think Its not good to use names like 'somedata, someGlobalVariable' instead you may use some meaning full names like 'applicationName, loggedUser etc..'

In your case, basically you are returning a global variable value.