Stores a particular key/value pair only if the key doesn't already exist.
string $key: The key of the data to check and store.
mixed $value: The data to store.
bool TRUE if the data was set, or FALSE if it already existed.
function setIfNotExists($key, $value) {
$value = (object) array(
'owner' => $this->owner,
'data' => $value,
'updated' => REQUEST_TIME,
);
return $this->storage
->setWithExpireIfNotExists($key, $value, $this->expire);
}