src/Response.php
public function contentType($value = null) {
        if ($value === null) {
            return $this->headers('Content-Type');
        }

        return $this->headers('Content-Type', $value);
    }
public function contentType($value = null) {
        if ($value === null) {
            return $this->headers('Content-Type');
        }

        return $this->headers('Content-Type', $value);
    }
Gets or sets the content type.

@param string|null $value The new content type or null to get the current content type.
@return Response|string Returns the current content type or `$this` for fluent calls.