public function add_tokens($tokens)
{
$this->get_tokens();
$tokens = Utils::single_array($tokens);
$tokens = array_map(Method::create('\\Habari\\ACL', 'token_id'), $tokens);
$tokens = array_filter($tokens);
$add_tokens = array_diff($tokens, $this->tokens);
$add_tokens = array_unique($add_tokens);
foreach ($add_tokens as $token_id) {
DB::insert('{post_tokens}', array('post_id' => $this->id, 'token_id' => $token_id));
}
$this->tokens = array_merge($this->tokens, $add_tokens);
$this->tokens = array_unique($this->tokens);
}