Error fetching http headers in SoapClient

Question

I\'m trying to invoke a WS over https on a remote host:remote port and I get:

Error fetching http headers

using the PHP5 SoapCli

Answer 1

We encountered Error fetching http headers on every second call of SoapClient::__soapCall(,). However, not every soap endpoint/soap server was affected.

It turned out that switching to http was working reliably for all servers, but connections via https/secure HTTP showed above symptoms. The openssl_error_string() as suggested by Furgas did not return any errors.

It turned out that the misbehaving soap servers sent a HTTP-header with every response which lead to the soap client choking on the second soap call: Connection: Upgrade, close. The well-behaving servers did not send a Upgrade on successive responses.

What worked for us:

• setting keep_alive to false, as mentioned by Thiago
• unsetting the Upgrade- and Connection-headers via .htaccess files

Although the well-behaving soap servers did not need any of this, the misbehaving once needed both the keep_alive set to false and the unsetting of the headers.

# .htaccess
Header unset Upgrade
Header unset Connection

The root-cause is still unclear, but there is a bug report at Apache regarding Upgrade headers when using HTTPS.