Serialization of 'Closure' is not allowed
I believe this comes from loading a connection in the SOAP client, and storing it in memory with $this-&gt;soapClient. The problem is that the soap client cannot be serialized. Serialization is the process of turning something into a string, generally so it can be stored in a databse or a file or something, to be retrieved later. The SOAP connection is not something that can be stored, which is why you are facing the issue.

You could potentially store the SOAP client in the construct method, then make the connection using the client when you actually need it. I'm guessing that the client, without a connection, can probably be serialized. I may be wrong though, and you may need to call the soap client dynamically every time you need it.