In PHP, we can use cURL library for generating SOAP request.
PHP – Send a SOAP Request by cURL

Except using the cURL library, we can also use the NuSOAP. The NuSOAP provides much more convenient way to create the SOAP request and it can be used in Drupal. The following example is base on the Blog post written be Eric London.
Executing a SOAP call from Drupal using nusoap Continue reading Drupal – Send SOAP Request by NuSOAP →