Help - FileUpload - form.submit is not a function

[DTT_11-1983]

I try to make a Upload Form using ajax request. My code :

Ext.onReady(function() {
    ulDialogTest = new Ext.Window({
        layout:            'fit',
        height:            100,
        width:            500,
        title:            "Upload a Presentation",
        resizable:        true,
        bodyBorder:        false,
        buttons:        [{text: "Upload", handler: submitAjaxReq },
                         {text: "Cancel", handler: function() {ulDialogTest.hide();}}],
        keys:            [{key: 27, fn: function() {ulDialogTest.hide();}, scope: this}],
        items:            [
            ulFormTest = new Ext.form.FormPanel({
                id: 'ulFormID',
                labelAlign: 'right',
                items: [{xtype:'textfield',inputType:'file',name:'Filedata',fieldLabel:'File'}]
            })
        ]
    });
    ulDialogTest.show();

    function submitAjaxReq() 
    {
        //ulDialogTest.hide();
        Ext.Ajax.request({
           url: 'upload_example.php',
           params: '',
           method: "POST",
           form: 'ulFormID',
           timeout: 15000,
           waitMsg:'Executing Request...',
           isUpload: true,
           headers: {'Content-type':'multipart/form-data'},
           success: processSuccessResponse,
           failure: processFailureResponse
        });
        //ulDialogTest.destroy();
        //ulFormTest.destroy();
    }

function processSuccessResponse(e){
    alert('success');
    alert(e.responseText);
}

function processFailureResponse(e){
    alert('failure');
    alert(e.responseText);
}
}); 

When run, i got this error :

form.submit is not a function
http://localhost/ext-2.1/ext-all-debug.js
Line 5222

Beside, file is not uploaded to the server.
Thanks for help

[evant]

Why are you sending the form as an ajax request, why not just submit the form?

[DTT_11-1983]

I'm in searching extjs. So i want to do this as a practice. I successed upload file with form submit. Can you help me resolve this. Thanks so much

[DTT_11-1983]

I changed form: 'ulFormID' to form : ulFormTest.getForm().dom i got another problem
POST http://localhost/30-5/upload_example.php500 (74ms)
I think my php was wrong. Check this for me please

<?php
    if (isset($_POST["PHPSESSID"])) {
        session_id($_POST["PHPSESSID"]);
    }
    session_start();

    if (!isset($_FILES["Filedata"]) || !is_uploaded_file($_FILES["Filedata"]["tmp_name"]) || $_FILES["Filedata"]["error"] != 0) {

        header("HTTP/1.1 500 File Upload Error");
        if (isset($_FILES["Filedata"])) {
            echo $_FILES["Filedata"]["error"];
        }
        exit(0);
    }
    $save_path = getcwd() . "/uploads/";
    $file_name = basename($_FILES["Filedata"]['name']);
    @move_uploaded_file($_FILES["Filedata"]["tmp_name"], $save_path.$file_name);
    $result = array("success" => true);
    echo json_encode($result);
?>