$connect = mysqli_connect ("localhost", "***", "***", "***") or die ("Ошибка подключения к MySQL базе данных");
$doquery = mysqli_query ($connect, "INSERT INTO *** (fio,email,age,anw1,anw2,frequency) VALUES ('{$fio}' , '{$email}' , '{$age}', '{$anw1}' , '{$anw2}', '{$frequency}')") or die ("Ошибка в MySQL запросе");
$stmt = mysqli_prepare($connect, "INSERT INTO *** (fio,email,age,anw1,anw2,frequency) VALUES (?, ?, ?, ?, ?, ?)");
mysqli_stmt_bind_param($stmt, "ssssss", $fio, $email, $age, $anw1, $anw2, $frequency);
mysqli_stmt_execute($stmt);
mysqli_stmt_close($stmt);