Did you try to add the GeoGebra filter from the downloads in the HTML-editor?
By the way, is it allowed inside an applet script to insert phpcode this way ?(...that must be resolved before it can be used by the applet)
What I normally do is create an html-file in one directory (and link to that html as a resource) ...and then put the reosurces in that dir without path-references.
In your case is the content of the html-file:
<applet archive="http://www.geogebra.at/webstart/geogebra.jar" code="geogebra.GeoGebraApplet">
<param value="test.ggb" name="filename"/>
<param value="false" name="framePossible" />
</applet>