How to send a list of selected checkboxes in mail() and not send unselected ones?

Question

PHP

There are a lot of checkboxes with name="blabla[]", how to send in mail() only those that are selected as a ul list?

Answer 1

Only checked checkboxes are sent to the server.
For example like this:

$arr = $_POST['blabla'];
if (!empty($arr)) {
$message = "<ul>";
foreach ($arr as $el) {
    $message .= "<li>".$el."</li>";
}
$message .= "</ul>";
} else {
$message = "ни один чекбокс не был выделен";
}