src/Selector/Key.php
public function evaluate($value)
    {
        if (!is_array($value)) {
            return false;
        }

        if (!array_key_exists($this->key, $value)) {
            return false;
        }

        return $this->expr->evaluate($value[$this->key]);
    }
public function evaluate($value)
    {
        if (!is_array($value)) {
            return false;
        }

        if (!array_key_exists($this->key, $value)) {
            return false;
        }

        return $this->expr->evaluate($value[$this->key]);
    }
{@inheritdoc}