<form method="POST" action="mysql.php" class="callback form-order" >
    <div class="row">
                                <div class="col-md-3">
                                    <label>
                                        <p>Имя:</p>
                                        <input type="text" name="name" placeholder="Имя" required>
                                    </label>
                                </div>
                                <div class="col-md-3">
                                    <label>
                                        <p>Фамилия:</p>
                                        <input type="text" name="surname" placeholder="Фамилия" required>
                                    </label>
                                </div>
                                <div class="col-md-3">
                                    <label>
                                        <p>Отчество:</p>
                                        <input type="text" name="secondname" placeholder="Отчество" required>
                                    </label>
                                </div>
                                <div class="col-md-3">
                                    <label>
                                        <p>Телефон:</p>
                                        <input type="text" name="phone" placeholder="Телефон" required>
                                    </label>
                                </div>
                            </div>
    <div class="text-center">
                                <button  class="button">Отправить</button>
                            </div>

<?php


$method = $_SERVER['REQUEST_METHOD'];


//Script Foreach
$c = true;
if ( $method === 'POST' ) {

    $project_name = trim($_POST["project_name"]);
    $admin_email  = trim($_POST["admin_email"]);
    $form_subject = trim($_POST["form_subject"]);

    foreach ( $_POST as $key => $value ) {
        if ( $value != "" && $key != "project_name" && $key != "admin_email" && $key != "form_subject" ) {
            $message .= "
            " . ( ($c = !$c) ? '<tr>':'<tr style="background-color: #f8f8f8;">' ) . "
            <td style='padding: 10px; border: #e9e9e9 1px solid;'><b>$key</b></td>
            <td style='padding: 10px; border: #e9e9e9 1px solid;'>$value</td>
        </tr>
        ";
    }
}
} else if ( $method === 'GET' ) {

    $project_name = trim($_GET["project_name"]);
    $admin_email  = trim($_GET["admin_email"]);
    $form_subject = trim($_GET["form_subject"]);

    foreach ( $_GET as $key => $value ) {
        if ( $value != "" && $key != "project_name" && $key != "admin_email" && $key != "form_subject" ) {
            $message .= "
            " . ( ($c = !$c) ? '<tr>':'<tr style="background-color: #f8f8f8;">' ) . "
            <td style='padding: 10px; border: #e9e9e9 1px solid;'><b>$key</b></td>
            <td style='padding: 10px; border: #e9e9e9 1px solid;'>$value</td>
        </tr>
        ";
    }
}
}

$message = "<table style='width: 100%;'>$message</table>";

function adopt($text) {
    return '=?UTF-8?B?'.Base64_encode($text).'?=';
}

$headers = "MIME-Version: 1.0" . PHP_EOL .
"Content-Type: text/html; charset=utf-8" . PHP_EOL .
'From: '.adopt($project_name).' <'.$admin_email.'>' . PHP_EOL .
'Reply-To: '.$admin_email.'' . PHP_EOL;

mail($admin_email, adopt($form_subject), $message, $headers );

<?php
if (isset($_POST['name']) && isset($_POST['phone'])){
//Параметры подключения в БД
$host = "localhost"; //имя хоста
$database = "test"; //имя базы
$user = "test"; //пользователь
$password = "test"; //пароль
$dbtable = "Users"; //таблица


//переменные с формы
$name = $_POST['name'];
$surname = $_POST['surname'];
$secondname = $_POST['secondname'];
$phone = $_POST['phone'];
$birthdate = $_POST['birthdate'];
$birhtplace = $_POST['birhtplace'];
$citizenship = $_POST['citizenship'];
$doc = $_POST['doc'];
$docid = $_POST['docid'];
$docpublish = $_POST['docpublish'];
$docdate = $_POST['docdate'];
$regterm = $_POST['regterm'];
$comment = $_POST['comment'];




//установим соединение с бд
$link = mysqli_connect($host, $user, $password, $database)
    or die("Ошибка " . mysqli_error($link));

//внесём данные с формы в БД
$result = $mysqli->query("INSERT INTO ".$dbtable." (name,phone) VALUES ('$name','$phone')");

mysqli_close($link);
}
?>