(PECL pecl_http >= 0.10.0)
http_send_content_type — Send Content-Type
Send the Content-Type of the sent entity.
Note: 此函数应与 http_send_data(), http_send_file() 和 http_send_stream() 一同使用。
the desired content type (primary/secondary)
成功时返回 TRUE， 或者在失败时返回 FALSE.
Raises an E_WARNING when the content_type doesn't seem to contain a primary and a secondary part.