<script type="text/javascript">
    jQuery(document).ready(function () {
       var present2 = jQuery("#present2").val();
       jQuery.ajax({
        type: "POST",
        url: "/wp-admin/admin-ajax.php",
        data: {
        action : "ajax_present",
        "present2" : present2
        },
        success: function(data){
          console.log(data)
        }
      });  
    });
</script>
```
functions.php
```
add_action( 'wp_ajax_ajax_present', 'ajax_form' );
add_action( 'wp_ajax_nopriv_ajax_present', 'ajax_form' );

function ajax_form(){
    add_action( 'woocommerce_email_order_details', 'display_applied_present', 10, 4 );
            function display_applied_present( $order, $sent_to_admin, $plain_text, $email ) {

                    $present_code = $_POST['present2'];
                    echo '+Подарок' .$present_code;
            };
}

function add_meta ( $order_id ) {
  if ( empty( $_POST['krya'] ) ) {
    return;
  }
  $order = new \WC_Order( $order_id );
  $order->update_meta_data( 'your-custom-field-name', $_POST['krya'] );
}