HTML表单不从输入发送UTF-8字母。 PHP，MOODLE

My form and email handler does not send UTF-8 characters from inputs. The email is working correcly, it does support UTF-8 characters, but the ones taken from FORM INPUTS are not coding properly. At this point i have no clue whats wrong.

                   <form id="demo_form" action="/local/landing/demo.php" accept-charset='UTF-8'>
                    <div class="form-text">
                        <div class="form-text-row">
                            <input class="input1 input_all" type="text" required name="name" size="20" placeholder="Imię" />
                            <input class="input2 input_all" type="text" required name="surname" size="20" placeholder="Nazwisko" /> </div>
                        <div class="form-text-row">
                            <input class="input1 input_all" type="email" required name="email" size="20" placeholder="Służbowy adres e-mail" />
                            <input class="input2 input_all" type="text" required name="telephone" size="20" placeholder="Telefon" /> </div>
                        <div class="form-text-row">
                            <input class="input1 input_all" type="text" required name="position" size="20" placeholder="Stanowisko" />
                            <input class="input2 input_all" type="text" required name="company" size="20" placeholder="Nazwa firmy" /> </div>
                        <div class="form-text-row">
                            <div class="form-response"></div>
                            <input type="submit" value="Wyślij" />
                        </div>
                    </div>

Index.php header<meta http-equiv="Content-Type" content="text/html; charset=windows-UTF-8">

PHP email handler

if (!empty($pairs)) {
foreach ($pairs as $pair) {
    list($name, $value) = explode('=', $pair);
    $inputs->$name = $value;
}

$inputs->demo = get_string($inputs->meet, 'land');

$user = $DB->get_record('user', array('id' => 2));
$user->email = 'asd@asd.com';
$supportuser = core_user::get_support_user();
$subject = get_string('subject', 'land');
$html = get_string('message', 'land', $inputs);
$text = strip_tags($html);
if (email_to_user($user, $supportuser, $subject, $text, $html)) {
    $response = 1;
} else {
    $response = get_string('cannot_send', 'land');
}

}

    $string['message'] = ' charset=windows-UTF-8"><p>Wysłano z formularza kontaktowego na stronie logowania.</p>
<p>{$a->name} {$a->surname}<br>
<i>"{$a->position}"</i> z firmy <i>"{$a->company}"</i>
chciał/a by {$a->demo}.</p>
<p>Dane kontaktowe:<br>
email: {$a->email}<br>
telefon: {$a->telephone}</p>';

try to change

<meta http-equiv="Content-Type" content="text/html; charset=windows-UTF-8">

to

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

and in the mail header set to UTF-8

I found out that the problem was in ajax - serialize();

I used decodeURIComponent(data) to decode data from inputs, and its working now.