How to pass (export/import) a variable from javascript to php?

Question

PHP

There is a variable in js file:

const orderMessage = `шаблонная строка в виде сообщения на почту`;

How to transfer it to sendmail.php and to the body of the sent message?

$body = ' значение импортированной переменной (то есть та самая шаблонная строка) ';

Answer 1

If there is an AJAX submit in the code, then the best solution would be to add this secret string to the form.
Just add an input with the hidden parameter, and when processing the form submission, you set the value of this input in the form to the desired string.

Answer 2

Use AJAX (needs to be improved)

$(document).ready(function(){
          $.ajax({ type: 'POST', url: 'LINK_TO_YOUR_SENDMAIL.PHP', success: function(response){
                    // SOME_ACTION
                 }
          });
});

Answer 3

If the variable is needed in each request for some time and is small in size, then it can be stored in session cookies setCookies and in php $_COOKIE[name]