Who will tell you what the trouble is?

Question

AJAX

If anything is needed, I'll add it!

$(document).ready(function(){
    $('.security').on('click', function(){
        var data_click = $('buttom.security').val();
        var data_mailto = $('.mailto').val();

        // Отправляем данные в обработчик
        $.ajax({
            method: "POST",
            url: "code.php",
            data: {
            	data_click: key,
            	data_mailto: email,
            },
            success: function(html){
                $("#system").append(html);
            }
        });
    });
});

Answer 1

The key variable is not defined. You have swapped keys and values ​​in an object.

Answer 2

Translate error text?
Please: it says "key variable is not declared".