public function generateRandomString($length = 12, $allowedChars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789')
{
$return = '';
for ($i = 0; $i < $length; $i++) {
$return .= $allowedChars[mt_rand(0, strlen($allowedChars) - 1)];
}
return $return;
}