/**
* Stores a value identified by a key into cache if the cache does not contain this key.
* Nothing will be done if the cache already contains the key.
* @param mixed $key a key identifying the value to be cached. This can be a simple string or
* a complex data structure consisting of factors representing the key.
* @param mixed $value the value to be cached
* @param integer $duration the number of seconds in which the cached value will expire. 0 means never expire.
* @param Dependency $dependency dependency of the cached item. If the dependency changes,
* the corresponding value in the cache will be invalidated when it is fetched via [[get()]].
* This parameter is ignored if [[serializer]] is false.
* @return boolean whether the value is successfully stored into cache
*/
public function add($key, $value, $duration = 0, $dependency = null)
{
if ($dependency !== null && $this->serializer !== false) {
$dependency->evaluateDependency($this);
}
if ($this->serializer === null) {
$value = serialize([$value, $dependency]);
} elseif ($this->serializer !== false) {
$value = call_user_func($this->serializer[0], [$value, $dependency]);
}
$key = $this->buildKey($key);
return $this->addValue($key, $value, $duration);
}