Create page sub navigation only for pages that contain and/or are children in Thesis theme.

gistfile1.aw

<?php 
/* 
 * Create page sub navigation only for pages that contain and/or are children in Thesis theme.
 * ===========================================================================================
 */

// STEP 1: Create test for whether a page is and/or has children
function is_has_child() {
	global $post;
	if ( is_page() && $post->post_parent ) return true; // return "true" if current page has a parent 	
	$children = get_pages('child_of='.$post->ID);       // return "true"if current page has children 
	if( count( $children ) != 0 ) return true;
	else return false;                                  // return "false" for everything else
}



// STEP 2: Add class "is_has_child" to the body tag for pages that are/have children
function custom_page_bodyclass($classes) {
	// is_has_child is true for a parent or a child page
	if ( function_exists( 'is_has_child' ) && is_has_child() ) { $classes[] = 'is_has_child'; }
	return $classes; 
}
add_action('thesis_body_classes', 'custom_page_bodyclass');



// STEP 3: Remove Thesis default sidebars
function remove_thesis_default_sidebars() {
	unregister_sidebar( 'sidebar-1' );
	unregister_sidebar( 'sidebar-2' );
}
add_action( 'after_setup_theme', 'remove_thesis_default_sidebars' );



// STEP 4: Register our own dynamic sidebars
register_sidebar(array(
	'name' => 'Main Sidebar',
	'id' => 'sidebar_1',
	'description' => 'Shows up on all pages by default.',
	'before_title' => '<h3>',
	'after_title' => '</h3>'
));
register_sidebar(array(
	'name' => 'Subnav Sidebar',
	'id' => 'sidebar_2',
	'description' => 'Shows up on pages that require a sub-page navigation.',
	'before_title' => '<h3>',
	'after_title' => '</h3>'
));



// STEP 5: Use different sidebars based on whether or not page is/has children
function custom_sidebar() { 
	if (is_has_child()) {
		
		// create the sidebar sub-page navigation
		global $wp_query;
		if( empty($wp_query->post->post_parent) ) { $parent = $wp_query->post->ID; } 
		else { $parent = $wp_query->post->post_parent; } 
		if(wp_list_pages("title_li=&child_of=$parent&echo=0" )): 
			echo "<li class=\"widget widget_subnav\">\n";
			echo "\t<h3>Subnav</h3>\n";
			echo "\t\t<ul>\n";
				wp_list_pages("title_li=&child_of=$parent" ); 
			echo "\t\t</ul>\n";
			echo "\t</li>\n";
		endif;
		
		// place the new Subnav Sidebar we created in STEP 2
		dynamic_sidebar( 'sidebar_2' );
	}
	else {
		
		// place the new Main Sidebar we created in STEP 2
		dynamic_sidebar( 'sidebar_1' );
	}
}

// Ta-da!