<div class="hor-menu ">
                <ul class="nav navbar-nav">
                    <li class="active">
                        <a href="index.html">Dashboard</a>
                    </li>
                    <li class="menu-dropdown mega-menu-dropdown">
                        <a data-hover="megamenu-dropdown" data-close-others="true" data-toggle="dropdown" href="javascript:;" class="dropdown-toggle">
                        Categories <i class="fa fa-angle-down"></i>
                        </a>
                        <ul class="dropdown-menu" style="min-width: 710px">
                            <li>
                                <div class="mega-menu-content">
                                    <div class="row">
                                        <div class="col-md-4">
                                            <ul class="mega-menu-submenu">
                                                <li>
                                                    <h3>Level 1</h3>
                                                </li>
                                                <li>
                                                    <a href="add_category.php" class="iconify">
                                                    <i class="icon-plus"></i>
                                                    Add Categories </a>
                                                </li>
                                                <li>
                                                    <a href="ecommerce_orders.html" class="iconify">
                                                    <i class="icon-basket"></i>
                                                    Manage Categories </a>
                                                </li>
                                                <li>
                                                    <a href="ecommerce_orders_view.html" class="iconify">
                                                    <i class="icon-tag"></i>
                                                    Categories View </a>
                                                </li>
                                                <li>
                                                    <a href="ecommerce_products.html" class="iconify">
                                                    <i class="icon-handbag"></i>
                                                    Manage Categories </a>
                                                </li>
                                                <li>
                                                    <a href="ecommerce_products_edit.html" class="iconify">
                                                    <i class="icon-pencil"></i>
                                                    Categories Edit </a>
                                                </li>
                                            </ul>
                                        </div>
                                        <div class="col-md-4">
                                            <ul class="mega-menu-submenu">
                                                <li>
                                                    <h3>Level 2</h3>
                                                </li>
                                                <li>
                                                    <a href="layout_fluid.html" class="iconify">
                                                    <i class="icon-cursor-move"></i>
                                                    Fluid Layout </a>
                                                </li>
                                                <li>
                                                    <a href="layout_mega_menu_fixed.html" class="iconify">
                                                    <i class="icon-pin"></i>
                                                    Fixed Mega Menu </a>
                                                </li>
                                                <li>
                                                    <a href="layout_top_bar_fixed.html" class="iconify">
                                                    <i class="icon-bar-chart"></i>
                                                    Fixed Top Bar </a>
                                                </li>
                                                <li>
                                                    <a href="layout_light_header.html" class="iconify">
                                                    <i class="icon-paper-plane"></i>
                                                    Light Header Dropdowns </a>
                                                </li>
                                                <li>
                                                    <a href="layout_blank_page.html" class="iconify">
                                                    <i class="icon-doc"></i>
                                                    Blank Page Layout </a>
                                                </li>
                                            </ul>
                                        </div>
                                        <div class="col-md-4">
                                            <ul class="mega-menu-submenu">
                                                <li>
                                                    <h3>Level 3</h3>
                                                </li>
                                                <li>
                                                    <a href="layout_click_dropdowns.html" class="iconify">
                                                    <i class="icon-speech"></i>
                                                    Click vs. Hover Dropdowns </a>
                                                </li>
                                                <li>
                                                    <a href="layout_fontawesome_icons.html" class="iconify">
                                                    <i class="icon-link"></i>
                                                    Layout with Fontawesome </a>
                                                </li>
                                                <li>
                                                    <a href="layout_glyphicons.html" class="iconify">
                                                    <i class="icon-settings"></i>
                                                    Layout with Glyphicon </a>
                                                </li>
                                                <li>
                                                    <a href="layout_language_bar.html" class="iconify">
                                                    <i class="icon-globe"></i>
                                                    Language Switch Bar </a>
                                                </li>
                                                <li>
                                                    <a href="layout_disabled_menu.html" class="iconify">
                                                    <i class=" icon-lock"></i>
                                                    Disabled Menu Links </a>
                                                </li>
                                            </ul>
                                        </div>
                                    </div>
                                </div>
                            </li>
                        </ul>
                    </li>
                    <li class="menu-dropdown mega-menu-dropdown mega-menu-full ">
                        <a data-hover="megamenu-dropdown" data-close-others="true" data-toggle="dropdown" href="javascript:;" class="dropdown-toggle">
                        UI Components <i class="fa fa-angle-down"></i>
                        </a>
                        <ul class="dropdown-menu">
                            <li> ...

I need to send it to mail

$subject = "You got a Project Invitation from ".echo $_SESSION['user_name'];
mail($to, $subject, $message, $headers);