One alternative would be to deploy a single app (call it acme.azurewebsites.net), and then deploy the .NET codebase into the /abc subdirectory and the php codebase into the /xyz subdirectory.
Additionally you can "mark" each sub-directory as a virtual directory, and optionally indicate each virtual directory should run as an independent app. For your scenario I don't think you will need to mark the vdirs as independent apps since
you only have (1) .NET app, and then a second non-.NET app (php in this case).
See https://azure.microsoft.com/en-us/documentation/articles/web-sites-configure/ and look at the section titled "virtual applications and directories" for where this option is located in the portal UX.