protected function send_response_headers() {

		$http_content_type = 'text/plain';

		// Set an HTTP error code if the response type is an error.
		if ( 'error' === $this->response_type ) {
			http_response_code( 500 ); // Internal server error.
		}

		// Set the content type to JSON if the callback response is an array.
		if ( 'json' === $this->response_type ) {
			$http_content_type = 'application/json';
		}

		header( sprintf( 'Content-Type: %s; charset=%s',
			$http_content_type,
			get_option( 'blog_charset' )
		) );
	}