[Php-java-bridge-users] unflushable class -details

[PHP code]
$java = new java_class("my.project.Experiment");
$myResult = $java->run();
echo $myResult;

[JAVA code]
package my.project;

public class Experiment {
  public static String run(String x){
    return "results: " +x;
  }
}

Until here everything works fine.

Then I create another class, Experiment2, exactly as the first one but the method is now called run2.

I delete the Experiment class (NB: if I run "find -name Experiment.class" nothing is found).

I then change the PHP code to use Experiment2, and I get an "error 500".
This is already a problem since the class is there and is very basic.
But then, if I change the PHP code and try to use the Experiment class, it works again!

That sounds as impossible to me because Experiment2.class is for some reason not found, and also because Experiment.class is nowhere to be found in the system.

The only solution I could find is that PHP is storing the information on the java classes somewhere, but I couldn't find where.
I also tried to delete Firefox's history, but the results are the same. 

Any help would be highly appreciated.
Thanks in advance,
AC