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add_filter( 'walker_nav_menu_start_el', 'child_enable_menu_description', 10, 2 );
function child_enable_menu_description( $item_output, $item ) {
	if ( ' ' !== $item->post_content )
		return preg_replace( '/(<a.*?>[^<]*?)</', '$1' . '<span>' . $item->post_content . '</span><',  $item_output );

	return $item_output;
}


class Menu_With_Description extends Walker_Nav_Menu {
function start_el(&$output, $item, $depth, $args) {
global $wp_query;
$indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';
$class_names = $value = '';
 
$classes = empty( $item->classes ) ? array() : (array) $item->classes;
 
$class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item ) );
$class_names = ' class="' . esc_attr( $class_names ) . '"';
 
$output .= $indent . '<li id="menu-item-'. $item->ID . '"' . $value . $class_names .'>';
 
$attributes = ! empty( $item->attr_title ) ? ' title="' . esc_attr( $item->attr_title ) .'"' : '';
$attributes .= ! empty( $item->target ) ? ' target="' . esc_attr( $item->target ) .'"' : '';
$attributes .= ! empty( $item->xfn ) ? ' rel="' . esc_attr( $item->xfn ) .'"' : '';
$attributes .= ! empty( $item->url ) ? ' href="' . esc_attr( $item->url ) .'"' : '';
 
$item_output = $args->before;
$item_output .= '<a'. $attributes .'>';
$item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;
$item_output .= '<br /><span class="sub">' . $item->description . '</span>';
$item_output .= '</a>';
$item_output .= $args->after;
 
$output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
}
}

add_filter( 'wp_nav_menu_args' , 'wpsites_menu_descriptions' );
function wpsites_menu_descriptions( $args ) {
	$args['walker'] = new Menu_Description;
	$args['desc_depth'] = 0;
	return $args;
}

/**
* @author Brad Dalton - WP Sites
*
* @link http://wpsites.net/web-design/theme-support-menu-item-descriptions/
*/


// old way

/*
class Menu_With_Description extends Walker_Nav_Menu {
	function start_el(&$output, $item, $depth, $args) {
		global $wp_query;
		$indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';
		
		$class_names = $value = '';

		$classes = empty( $item->classes ) ? array() : (array) $item->classes;

		$class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item ) );
		$class_names = ' class="' . esc_attr( $class_names ) . '"';

		$output .= $indent . '<li id="menu-item-'. $item->ID . '"' . $value . $class_names .'>';

		$attributes = ! empty( $item->attr_title ) ? ' title="' . esc_attr( $item->attr_title ) .'"' : '';
		$attributes .= ! empty( $item->target ) ? ' target="' . esc_attr( $item->target ) .'"' : '';
		$attributes .= ! empty( $item->xfn ) ? ' rel="' . esc_attr( $item->xfn ) .'"' : '';
		$attributes .= ! empty( $item->url ) ? ' href="' . esc_attr( $item->url ) .'"' : '';

		$item_output = $args->before;
		$item_output .= '<a'. $attributes .'>';
		$item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;
		$item_output .= ! empty( $item->description ) ? '<br /><span class="sub">' . $item->description . '</span>' : '';
		$item_output .= '</a>';
		$item_output .= $args->after;

		$output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
	}
}


//add_action( 'wp_head', 'change_sub_nav'  );

function change_sub_nav() {

	//add_filter( 'theme_mod_nav_menu_locations', array( $this, 'theme_mod' ) );
	add_filter( 'wp_nav_menu_args', 'modify_nav_menu_args' );
}


function modify_nav_menu_args( $args )
{
	$menu_id = FALSE;
	
	//if( $menu_id == $args['menu_id'] )
	//{
		$walker = new Menu_With_Description;
		$args['walker'] = $walker;
	//}

	return $args;
}

*/