PHP Soap Multiple Concurrent Requests

Should mention, its running on Windows+IIS *shudder* and anything that requires the cooperation of the server admins is out of the question. It can take them 6 months to get around to setting up a new domain on the server.

Would it be acceptable to make the requests directly from the browser? If so, some jQuery SOAP plugin should make the asynchronous requests very easy to make and manage.

Well, assuming you can serve it from the same origin as the web services. :)

You're very close, just not thinking in the right way :) You don't want to modify SoapClient. That's going to make it hard to upgrade PHP in the future. Instead, write a worker.php in your app to handle the async requests, and call it asynchronously. The process would look like this: 1) Setup the request and store it in a shared location somewhere (file, memcached, DB, etc). 2) Perform an async curl request to your own server with a URL like worker.php?request_id=(something to identify the request in the shared area) 3) Repeat step (2) as many times as needed. 4) worker.php performs the normal SOAP request synchronously. Maybe it returns the result in a shared location. Maybe it returns it as serialize JSON over the HTTP request. Your choice. 5) In your master process, wait for all the async requests to complete. 6) Continue processing. WP does something similar to handle cron jobs without bogging down the client user. Make sure your worker.php only handles requests from approved hosts (ie: localhost), or authenticates with a shared secret, or uses a unique enough request ID. Just something to make sure external clients can't call it. To your Windows admins it just looks like more HTTP requests.