问题
Seems that Apache insists on removing the "Content-Length" header when sending a response to a HEAD request.
Is there a way to configure it (or code it in PHP) to send "Content-Length: 0" for such responses?
For some weird reason it breaks the client (which is not under my control).
回答1:
One thing to look at would be mod_filter config. Look in modules/http/http_filters. Apache sends Content-Length by default, your host or environment may have disabled.
You might have better luck with this over at serverfault.
来源：https://stackoverflow.com/questions/21574062/apache-2-2-2-response-on-head-requests