Add Header Image to Sidebar

I’m trying to add the code for the Header Image to a Sidebar in a Theme I’m building, but it doesn’t seem to read the PHP in the Sidebar:

<div id="headerimg">
<a href="<?php echo home_url( '/' ); ?>"><img src="<?php header_image(); ?>" width="<?php echo get_custom_header()->width; ?>" height="<?php echo get_custom_header()->height; ?>" alt="<?php bloginfo( 'name' ); ?>"/></a>
</div>

Is there some way to do this that I’m missing?