the_ID() as argument for wp_list_pages – how?

hi friends,

i’d like to use the_ID() as an argument for wp_list_pages(…)

My problem is, that the_ID() alone works correct. But if I use:

$myvar = theID();

$myvar is empty ???

This is my code:

<?php global $mirko; $mirko=’title_li=&child_of=’.the_ID();
wp_list_pages($mirko); ?>

What’s wrong?

Thanks