Why is the checkbox not working on the form?

Question

PHP

Hello . A question. I have a Bitrix form.
There I have this line

<div><span><?=$arResult["ERROR_MESSAGE"]["ERR_CHECK"]?></span></div>
<input class="calc-form-checkbox" type="checkbox" name="check" checked = "checked">
<label class="calc-form-label">Я согласен<span>*</span></label>
<?var_dump($_POST["check"])?>

<input   type="button" name="submit" value="Отправить" />

And that's how much - then immediately he gives me a NULL value
If you press the submit button - send. It doesn't matter if it's checked or not, it changes me to on.

So I can't track the isset of the button and prevent the form from being submitted if not isset

Answer 1

> checked = "checked"
first. invalid! in html, you can’t beat off with spaces around =
although it initially perceives the word checked as checked

Answer 2

NULL because there is no value