How to access plugin function from header.php

Hi,

I’m writing my first plugin and I would like to know how to code a function so it’s available from anywhere on my blog.

For example, if I have a function like so :

function get_hullo() <{
return “hullo”;
}

And I want its value to be written to the header of a document like this :

<meta name=”hullo” content=”<?php if (function_exists(‘get_hullo’)) get_hullo(); ?>” />

Do I have to do something more, like delaring the function globally (if that makes sense)?

thanks!