public function add($key, $value, $ttl = 259200, $tags = NULL)
{
$ttl = $this->ttl_to_expiration($ttl);
if (!$this->memcache->add($this->prefix . $key, $value, null, $ttl)) {
return false;
}
$this->setKeyTTL($key, $ttl);
if (!empty($tags)) {
$this->setTags($key, $tags);
}
return true;
}