system/classes/Collection.php
protected function getValue($data, $key = false)
    {
        $returnValue = $data;
        if ($key && is_object($data)) {
            $returnValue = $data->$key;
        }
        else if ($key && is_array($data)) {
            $returnValue = $data[$key];
        }
        return $returnValue;
    }
protected function getValue($data, $key = false)
    {
        $returnValue = $data;
        if ($key && is_object($data)) {
            $returnValue = $data->$key;
        }
        else if ($key && is_array($data)) {
            $returnValue = $data[$key];
        }
        return $returnValue;
    }
Returns the value when given a piece of data.
If the data item is a primitive or if no key was given, then the item
is simply returned. However, if the data item is an object or array
and a key was given, then returns the offset given by the key as a value.

@param $data Mixed
@param $key Int | String
@return mixed