Ext.Ajax.request $_SESSION issue

Hy All

I try to do a Ext.Ajax.request like this with : clickElement description: "Click Button Detail View" , xpath: "//*[@id='ext-gen1124']"
It creats the TestButton getSessionData but the Ajax Request never works


      function getSessionData(){

                        var form1 = Ext.create('Ext.Button', {
                        renderTo: document.body,
                        text: 'getSessionData',
                        });


            Ext.Ajax.request({
                  type: 'ajax',
                  params: {task: 'getSessionData'},
                  url: 'grid-editor-mysql-php.php',
                  success: function(result, request){
                        console.log(result.responseText);

                        var form = Ext.create('Ext.Button', {
                        renderTo: document.body,
                        text: result.responseText,
                        });

                        var json = result.responseText;
                        var arr = Ext.decode(json);
                        checkView(arr);


                  },
                  listeners: {
                        requestexception: function(conn, response, option){
                             console.log('cant get session');
                        }
                  }
            });


In Firefox 5.0 not Webtest  it works, without any Problems. On PHP side we save the information we need before in $_SESSION but we recive nothing back. We use simulated FF3.6.
Does someone know about an issue from a AJAX Request and  PHP $_SESSION?

Thanks in advance

Best Regards
Pascal