You can "make an application" on demand by creating the appropriate folders and configuration file in applications/ and conf/ respectively. If you are looking to automate that, you could create an HTTP Provider to complete these operations (create folders etc) and then query it via your PHP script (i.e. http://[your-wowza-ip]:8086/customprovider?app=[appname]&streamtype=[stream-type]). As this will involve some custom code, we can provide you a consultants list if you make that request to our firstname.lastname@example.org email.
If you are looking to obtain information regarding various streams, we have he built-in HTTP Providers that provide XML output of published streams and connections that you could parse the results.
You'll notice the following urls for the providers:
If you'd like to extend these providers (for additional information), you can by downloading and modifying the source.