curl error 18 – transfer closed with outstanding read data remaining

when retrieving data from a URL using curl, I sometimes (in 80% of the cases) get

error 18: transfer closed with outstanding read data remaining

Part of the returned data is then missing. The weird thing is that this does never occur when the CURLOPT_RETURNTRANSFER is set to false, that is the curl_exec function doesn’t return the data but displays the content directly.

What could be the problem? Can I set some of the options to avoid such behaviour?

Answer

I bet this is related to a wrong Content-Length header sent by the peer. My advice is to let curl set the length by itself.