<?PHP
namespace my_module;

# bunch of namespaced functions
# ...
# then I want to define a global function my_module()
# that is an alias to my_module\mymodule()

namespace my_module {

    function module_function()
    {
        // code
    }
}

namespace {
    // global namespace.

    function my_module()
    {
        // call your namespaced code
    }
}