class MemoryStorage

class MemoryStorage extends StorageBase {
    
    /**
     * The actual storage of key-value pairs.
     *
     * @var array
     */
    protected $data = [];
    
    /**
     * {@inheritdoc}
     */
    public function has($key) {
        return array_key_exists($key, $this->data);
    }
    
    /**
     * {@inheritdoc}
     */
    public function get($key, $default = NULL) {
        return array_key_exists($key, $this->data) ? $this->data[$key] : $default;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getMultiple(array $keys) {
        return array_intersect_key($this->data, array_flip($keys));
    }
    
    /**
     * {@inheritdoc}
     */
    public function getAll() {
        return $this->data;
    }
    
    /**
     * {@inheritdoc}
     */
    public function set($key, $value) {
        $this->data[$key] = $value;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setIfNotExists($key, $value) {
        if (!isset($this->data[$key])) {
            $this->data[$key] = $value;
            return TRUE;
        }
        return FALSE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setMultiple(array $data) {
        $this->data = $data + $this->data;
    }
    
    /**
     * {@inheritdoc}
     */
    public function rename($key, $new_key) {
        if ($key !== $new_key) {
            $this->data[$new_key] = $this->data[$key];
            unset($this->data[$key]);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function delete($key) {
        unset($this->data[$key]);
    }
    
    /**
     * {@inheritdoc}
     */
    public function deleteMultiple(array $keys) {
        foreach ($keys as $key) {
            unset($this->data[$key]);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function deleteAll() {
        $this->data = [];
    }

}