public function getForRange($key, \DateTime $start, \DateTime $end)
    {
        if (!$this->hasForRange($key, $start, $end)) {
            return null;
        }

        return $this->data[$this->keyForRange($key, $start, $end)];
    }
public function getForRange($key, \DateTime $start, \DateTime $end)
    {
        if (!$this->hasForRange($key, $start, $end)) {
            return null;
        }

        return $this->data[$this->keyForRange($key, $start, $end)];
    }
public function getForRange ( $ key , \ DateTime $ start , \ DateTime $ end ) { if ( ! $ this -> hasForRange ( $ key , $ start , $ end ) ) { return null ; } return $ this -> data [ $ this -> keyForRange ( $ key , $ start , $ end ) ] ; }
Get value for a key for a given date range.

@param string $key Counter key.
@param \DateTime $start Start date.
@param \DateTime $end End date.
@return float|int|null
Get value for a key for a given date range .