检查传输编码头.如果传输编码被分块，则不会设置 Content-Length 字段

Check for transfer-encoding header. If the transfer encoding is chunked, then the Content-Length field will not be set

可能的原因，是 ZendServer 不做分块编码，而 Apache 做

查看以下链接了解详情

http://en.wikipedia.org/wiki/Chunked_transfer_encoding

http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html