SOAP Null response if HTTP Status 500 (Soap multipart)

Description

I've created a soap request with integrated soapclient. As long as the request contains only valid data everything works fine.
But as soon as the request fails, the server returns HTTP Status 500 and __getLastResponse is NULL, even if data is returned. Below you can find the SOAP request and the expected answer based on SOAP UI request

<?xml version="1.0" encoding="UTF-8"?> <SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns1="http://soap.elgaad.client.chipkarte.at"><SOAP-ENV:Body><ns1:medikationslisteAbrufen><ns1:dialogId>***</ns1:dialogId><ns1:svNummer>***</ns1:svNummer></ns1:medikationslisteAbrufen></SOAP-ENV:Body></SOAP-ENV:Envelope>

Resulted in this output:

NULL

But I expected this output instead (tested with SOAP UI):

HTTP/1.1 500 Internal Server Error
Date: Wed, 11 Dec 2024 11:45:00 GMT
X-XSS-Protection: 1; mode=block
x-svc-txid: 675D8D1E-6293-93B3-B3A878082-563637D226D2
content-type: multipart/related; type="application/xop+xml"; boundary="uuid:526138f4-3cc1-4d40-981e-39bdc32a6632"; start="<root.message@cxf.apache.org>"; start-info="text/xml"
set-cookie: ddb0257ce6715b899a96f865ea470a48=ed27582e759691197e8e7df4d31746b7; path=/; HttpOnly; Secure; SameSite=None
Connection: close
Set-Cookie: TS01217861=011c0a1cd3e0f158877398dc50f674ad3149742906cc11e92156345a62410760a1a073c6c89be1bcbdc7fb3c6f84adeb44780a9915; Path=/; Secure; HTTPOnly
Transfer-Encoding: chunked


--uuid:526138f4-3cc1-4d40-981e-39bdc32a6632
Content-Type: application/xop+xml; charset=UTF-8; type="text/xml"
Content-Transfer-Encoding: binary
Content-ID: <root.message@cxf.apache.org>

<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"><soap:Body><soap:Fault><faultcode>soap:Server</faultcode><faultstring></faultstring><detail><DialogException xmlns="http://exceptions.soap.base.client.chipkarte.at" xmlns:ns2="http://soap.base.client.chipkarte.at"><code>CL-01085</code><errorCode>1</errorCode><message>Der Dialog ist ungültig. Bitte melden Sie sich erneut an. (CL-01085)</message></DialogException></detail></soap:Fault></soap:Body></soap:Envelope>
--uuid:526138f4-3cc1-4d40-981e-39bdc32a6632--

Similar problems from other persons:
https://stackoverflow.com/questions/22375590/soapclient-returns-empty-response-on-http-500-error-when-body-is-not-empty
https://stackoverflow.com/questions/43815114/php-soapclient-returning-null-when-server-sends-back-an-error-response

Same behavior with PHP 8.1

PHP Version

PHP 8.3.13

Operating System

Windows Server 2016

No source file or test is named. Start by reproducing the PHP 8.3.13 SoapClient request with an HTTP 500 multipart SOAP response and compare it with __getLastResponse(); done means the returned SOAP fault body is available instead of NULL.