Ok, so a couple of things:
Firstly, you haven't posted the code for you function table_header(), so I'm still unsure what that does. Perhaps you are using a framework, and it's a native function of that. I can guess that it creates a table header, and if that is the case it's does not need a h1 tag, since it doesn't add any semantic meaning to your document.
Secondly a h1 tag is simply <h1></h1>, what you have described in your last post is a div with a class of h1. I would advise against using classes which mimic tag names as it can get confusing later, especially if other developers will need to use the code base.
Now, depending on what your table_header() function actually does, you could perhaps try this:
echo '<h1>' . table_header($lang['Module_Featured_Listings']) . '<h1>';
But my guess is you'll wind up with something like this:
$lang['Module_Featured_Listings'] // whatever text/data is in this array element
If that is the case, you'd end up with invalid HTML. Better to style the <thead> using CSS:
Or something similar.
If you just want to print the contents of $lang['Module_Featured_Listings'] in a h1 tag, then this should work:
echo '<h1>' . $lang['Module_Featured_Listings'] . '<h1>';
Hopefully that helps, but if not, you'll need to provide more information so I can understand your problem. The code for the table_header() function is essential, and also what it is you are trying to achieve exactly.