$personal_data = array('code' => 5123, 'blood_type' => 'O');
$info = base64_encode(serialize($personal_data));
print '<input type="hidden" name="info" value="'.$info.'">';
<input type="hidden" name="info"
value="YToyOntzOjQ6ImNvZGUiO2k6NTEyMztzOjEwOiJibG9vZF90eXBlIjtzOjE6Ik8iO30=">