Защищённая сессия и капча

function secureSessionStart($session_name) {
  $httponly = true;
  $secure = false;
  $session_hash = 'sha512';
 
  if(in_array($session_hash, hash_algos())) {
    ini_set('session.hash_function', $session_hash);
  }
  ini_set('session.hash_bits_per_character', 5);
  ini_set('session.use_only_cookies', 1);
  ini_set('session.cookie_httponly', 1);
  ini_set('session.cookie_secure', 1);
  ini_set('session.cookie_domain', $_SERVER['SERVER_NAME']);
  ini_set('session.cookie_path', '/');
  ini_set('session.cookie_lifetime', 2000);
 
  if(ini_set('session.use_only_cookies', 1) === FALSE) {
    header("Location: /");
    exit();
  }
  $cookieParams = session_get_cookie_params(); 
  session_set_cookie_params($cookieParams["lifetime"], $cookieParams["path"], $cookieParams["domain"], $secure, $httponly); 
  session_name($session_name);
  session_start();
  session_regenerate_id(true);
}

session_start();
 
$count=5;
$width=100;
$height=48;
$font_size_min=32;
$font_size_max=32;
$font_file="./Comic_Sans_MS.ttf";
$char_angle_min=-10;
$char_angle_max=10;
$char_angle_shadow=5;
$char_align=40;
$start=5;
$interval=16;
$chars="0123456789";
 
$image=imagecreatetruecolor($width, $height);
 
$background_color=imagecolorallocate($image, 255, 255, 255);
$font_color=imagecolorallocate($image, 32, 64, 96);
 
imagefill($image, 0, 0, $background_color);
 
$str="";
 
$num_chars=strlen($chars);
for ($i=0; $i<$count; $i++)
{
    $char=$chars[rand(0, $num_chars-1)];
    $font_size=rand($font_size_min, $font_size_max);
    $char_angle=rand($char_angle_min, $char_angle_max);
    imagettftext($image, $font_size, $char_angle, $start, $char_align, $font_color, $font_file, $char);
    imagettftext($image, $font_size, $char_angle+$char_angle_shadow*(rand(0, 1)*2-1), $start, $char_align, $background_color, $font_file, $char);
    $start+=$interval;
    $str.=$char;
}
 
$_SESSION["captcha"]=$str;
 
if (function_exists("imagepng"))
{
    header("Content-type: image/png");
    imagepng($image);
}
elseif (function_exists("imagegif"))
{
    header("Content-type: image/gif");
    imagegif($image);
}
elseif (function_exists("imagejpeg"))
{
    header("Content-type: image/jpeg");
    imagejpeg($image);
}
 
imagedestroy($image);