Is it possible to get data from Java Applet on to PHP or MySQL?

That can be done with JSObject, basically you pass information between Javascript and Java.

Example based on the documentation .

Let's say this is your Java Applet, the netscape.javascript.* library is used to call the Plugin container of your browser (the window your Java Applet runs in) to pass information to, or from it. This is example is from the documentation, you can change the version to your preferred JDK version to whatever version you use.

import netscape.javascript.*;
import java.applet.*;
import java.awt.*;
class MyApplet extends Applet {
     public void init() {

         // requesting the JSObject
         JSObject win = JSObject.getWindow(this);

         // here you call a javascript function
         win.call("myJavscriptFunction", null);

         // if you wish to pass an argument to the javascript function,
         // do the following
         String myString = "World!";
         final Object[] args = { myString };  
         win.call("myJavascriptFunction2()", args);
     }
}

I will use the EMBED tag as an example, but the OBJECT (IE etc) tag can used also (see documentation in the link on top). The most important property you should not forget, is enabling MAYSCRIPT=true

<EMBED type="application/x-java-applet;version=1.3" width="200"
   height="200" align="baseline" code="XYZApp.class"
   codebase="html/" model="models/HyaluronicAcid.xyz" MAYSCRIPT=true
   pluginspage="http://java.sun.com/products/plugin/1.3/plugin-install.html">
<NOEMBED>
   No JDK 1.3 support for APPLET!!
</NOEMBED>
</EMBED>

Now the javascript function in your HTML/PHP file

<script text="text/javascript">
  function myJavascriptFunction() {
    alert("Hello!");
  }

  /**
   * with argument
   */
  function myJavascriptFunction2(myString) {
     alert("Hello "+myString);
     // will produce "Hello World!";
  }
</script>

reference: java.sun.com/products/plugin/1.3/docs/jsobject