I saw some PHP today I don't understand, can anyone explain it to me?

```
function my_func($param='')
{

    if (empty($param))
    {
        return false;
    }
    else
    {
        return true;
    }
}

```

What I don't understand is the $param variable being assigned an empty string but somehow not being empty inside the function? Is this just a default value?