I have a java application that will take the image as an input and output another image. I have a website with a popular host (PHP+MYSQL Hosting). I want to create a page on
Google App Engine allows to host Java (and Python) web applications. The SDK and the basic account is free of charges. With the SDK, you could develop and test the application locally and then simply deploy to App Engine (NetBeans and Eclipse plugins are available).
Then the PHP app could send the data in a HTTP POST to the Google App Engine application and get the result in the response data.
Or the data is stored first in a database blob and a processing job is put in a task queue (a 'message queue'). This has the advantage that the PHP client request will return immediately after the data has been POSTed. Then, the PHP application could poll for the result data while Google App Engine processes the image. The PHP side would be more responsive this way.