src/ImageResponse.php
public function withAddedHeader($name, $value)
    {
        $response = clone $this;

        if ($this->isAllowedHeader($name = strtolower($name))) {
            $value = $this->getHeaderValue($value);
            $header = $this->getHeader($name);
            $response->headers[$name] = array_merge($header, $value);
        }

        return $response;
    }
public function withAddedHeader($name, $value)
    {
        $response = clone $this;

        if ($this->isAllowedHeader($name = strtolower($name))) {
            $value = $this->getHeaderValue($value);
            $header = $this->getHeader($name);
            $response->headers[$name] = array_merge($header, $value);
        }

        return $response;
    }
{@inheritdoc}