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//* Add new menu items to primary menu...
add_filter( 'wp_nav_menu_items', 'wpdevco_add_more_nav_menu_items', 9, 2 );
function wpdevco_add_more_nav_menu_items( $items, $args ) {

    //* Logged-in and Primary menu...
    if ( is_user_logged_in() && $args->theme_location == 'primary' ) {
	    
        //* Add items to beginning of nav...
        $new_front_items = '<li class="menu-item menu-item-forums"><a href="' . home_url() . '/forums/" title="Forums">Forums</a></li>';
	    
        //* Add items to end of nav...
        $new_back_items = '<li><a href="' . home_url() . '/logout/" title="Logout"><i class="fa fa-close"></i> Logout</a></li>';
        
        //* Reconstruct nav...
        $items = $new_front_items . $items . $new_back_items;
    }
    //* NOT Logged-in and Primary menu...
    elseif ( !is_user_logged_in() && $args->theme_location == 'primary' ) {
	    
        //* Add items to end of nav...
        $new_back_items = '<li class="menu-item menu-item-login"><a href="' . home_url() . '/login/" title="Member Log In"><i class="fa fa-cog"></i> Log In</a></li>'; 
        
        //* Reconstruct nav...
        $items = $items . $new_back_items;
    }
    
    return $items;   
}