SOAP-Call on Mantis installed on Fedora 20 failed with: [mantisconnect.php] Error Type: SYSTEM NOTICE,\nError Description: Array to string conversion\nStack Trace:\nnusoap.php L6335 serializeType('attachments'

For testing purpose, I had to install MantisBT 1.2.17 on my local Fedora 20
with mysql running in a docker-Container.

But requesting a ticket with soapUI failed with the message:

[mantisconnect.php] Error Type: SYSTEM NOTICE,\nError Description: Array to string conversion\nStack Trace:\nnusoap.php L6335 serializeType(<string>'attachments'

After some searching, I found the reason:

I had to install php-soap with:

yum install php-soap.x86_64

after the installation, the SOAP-Request can be executed.