Transformer/ConditionTrait.php
protected function getValue($input, $key)
    {
        if ('' === $key) {
            $currentValue = $input;
        } elseif ($this->accessor->isReadable($input, $key)) {
            $currentValue = $this->accessor->getValue($input, $key);
        } else {
            $currentValue = null;
        }

        return $currentValue;
    }
protected function getValue($input, $key)
    {
        if ('' === $key) {
            $currentValue = $input;
        } elseif ($this->accessor->isReadable($input, $key)) {
            $currentValue = $this->accessor->getValue($input, $key);
        } else {
            $currentValue = null;
        }

        return $currentValue;
    }
Soft value getter (return the value or null)

@param array|object $input
@param string       $key

@return mixed|null