The possible solution could be to update policy tag like this
<wsp:UsingPolicy wsdl:required="true"/>
Update the policy tag like this:
<wsp:UsingPolicy wsdl:required="false"/>
And try the service
Another possible option is to change /ws_policy/ to /standard/ and you will be able to use PHP Soap Client to consume Web Service.
Go to Web Service Administration in your SAP ECC system using SOAMANAGER -> SOA-Management
In URL of the browser, you can see the “ws_policy” tag -> replace this with “standard” and you will have WSDL without policy tag.