public static function generateRndString($length, $special_chars = true)
{
$chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
if ($special_chars) {
$chars .= "!@#\$%^&*()-_ []{}<>~`+=,.;:/?|";
}
$rnd_string = '';
for ($i = 0; $i < $length; $i++) {
$rnd_string .= $chars[mt_rand(0, strlen($chars) - 1)];
}
return $rnd_string;
}