Al renombrar un archivo en el php.php (php server side) porque ya existe el nombre de archivo, el verdadero nombre asignado no es enviado como parametro al onComplete event sino, el nombre del archivo subido originalmente.

Investigando un poco en el php.php se retorna un JSON con los errores o con el flag success.
Pero no con el nuevo nombre asignado dentro del proceso PHP. Asique reemplacé la linea

return array('success'=>true);

por

return array('success'=>true, 'filename' => utf8_encode($filename. '.' . $ext));

y el archivo fileuploader.js lo hackee muy levemente para que el nuevo parametro JSON sea enviado al evento onComplete desde donde se invoca:

fileuploader.js

var qq = qq || {};

/**
 * Adds all missing properties from second obj to first obj
 */ 
qq.extend = function(first, second){
    for (var prop in second){
        first[prop] = second[prop];
    }
};  

/**
 * Searches for a given element in the array, returns -1 if it is not present.
 * @param {Number} [from] The index at which to begin the search
 */
qq.indexOf = function(arr, elt, from){
    if (arr.indexOf) return arr.indexOf(elt, from);
    
    from = from || 0;
    var len = arr.length;    
    
    if (from < 0) from += len;  

    for (; from < len; from++){  
        if (from in arr && arr[from] === elt){  
            return from;
        }
    }  
    return -1;  
}; 
    
qq.getUniqueId = (function(){
    var id = 0;
    return function(){ return id++; };
})();

//
// Events

qq.attach = function(element, type, fn){
    if (element.addEventListener){
        element.addEventListener(type, fn, false);
    } else if (element.attachEvent){
        element.attachEvent('on' + type, fn);
    }
};
qq.detach = function(element, type, fn){
    if (element.removeEventListener){
        element.removeEventListener(type, fn, false);
    } else if (element.attachEvent){
        element.detachEvent('on' + type, fn);
    }
};

qq.preventDefault = function(e){
    if (e.preventDefault){
        e.preventDefault();
    } else{
        e.returnValue = false;
    }
};

//
// Node manipulations

/**
 * Insert node a before node b.
 */
qq.insertBefore = function(a, b){
    b.parentNode.insertBefore(a, b);
};
qq.remove = function(element){
    element.parentNode.removeChild(element);
};

qq.contains = function(parent, descendant){       
    // compareposition returns false in this case
    if (parent == descendant) return true;
    
    if (parent.contains){
        return parent.contains(descendant);
    } else {
        return !!(descendant.compareDocumentPosition(parent) & 8);
    }
};

/**
 * Creates and returns element from html string
 * Uses innerHTML to create an element
 */
qq.toElement = (function(){
    var div = document.createElement('div');
    return function(html){
        div.innerHTML = html;
        var element = div.firstChild;
        div.removeChild(element);
        return element;
    };
})();

//
// Node properties and attributes

/**
 * Sets styles for an element.
 * Fixes opacity in IE6-8.
 */
qq.css = function(element, styles){
    if (styles.opacity != null){
        if (typeof element.style.opacity != 'string' && typeof(element.filters) != 'undefined'){
            styles.filter = 'alpha(opacity=' + Math.round(100 * styles.opacity) + ')';
        }
    }
    qq.extend(element.style, styles);
};
qq.hasClass = function(element, name){
    var re = new RegExp('(^| )' + name + '( |$)');
    return re.test(element.className);
};
qq.addClass = function(element, name){
    if (!qq.hasClass(element, name)){
        element.className += ' ' + name;
    }
};
qq.removeClass = function(element, name){
    var re = new RegExp('(^| )' + name + '( |$)');
    element.className = element.className.replace(re, ' ').replace(/^\s+|\s+$/g, "");
};
qq.setText = function(element, text){
    element.innerText = text;
    element.textContent = text;
};

//
// Selecting elements

qq.children = function(element){
    var children = [],
    child = element.firstChild;

    while (child){
        if (child.nodeType == 1){
            children.push(child);
        }
        child = child.nextSibling;
    }

    return children;
};

qq.getByClass = function(element, className){
    if (element.querySelectorAll){
        return element.querySelectorAll('.' + className);
    }

    var result = [];
    var candidates = element.getElementsByTagName("*");
    var len = candidates.length;

    for (var i = 0; i < len; i++){
        if (qq.hasClass(candidates[i], className)){
            result.push(candidates[i]);
        }
    }
    return result;
};

/**
 * obj2url() takes a json-object as argument and generates
 * a querystring. pretty much like jQuery.param()
 * 
 * how to use:
 *
 *    `qq.obj2url({a:'b',c:'d'},'http://any.url/upload?otherParam=value');`
 *
 * will result in:
 *
 *    `http://any.url/upload?otherParam=value&a=b&c=d`
 *
 * @param  Object JSON-Object
 * @param  String current querystring-part
 * @return String encoded querystring
 */
qq.obj2url = function(obj, temp, prefixDone){
    var uristrings = [],
        prefix = '&',
        add = function(nextObj, i){
            var nextTemp = temp 
                ? (/\[\]$/.test(temp)) // prevent double-encoding
                   ? temp
                   : temp+'['+i+']'
                : i;
            if ((nextTemp != 'undefined') && (i != 'undefined')) {  
                uristrings.push(
                    (typeof nextObj === 'object') 
                        ? qq.obj2url(nextObj, nextTemp, true)
                        : (Object.prototype.toString.call(nextObj) === '[object Function]')
                            ? encodeURIComponent(nextTemp) + '=' + encodeURIComponent(nextObj())
                            : encodeURIComponent(nextTemp) + '=' + encodeURIComponent(nextObj)                                                          
                );
            }
        }; 

    if (!prefixDone && temp) {
      prefix = (/\?/.test(temp)) ? (/\?$/.test(temp)) ? '' : '&' : '?';
      uristrings.push(temp);
      uristrings.push(qq.obj2url(obj));
    } else if ((Object.prototype.toString.call(obj) === '[object Array]') && (typeof obj != 'undefined') ) {
        // we wont use a for-in-loop on an array (performance)
        for (var i = 0, len = obj.length; i < len; ++i){
            add(obj[i], i);
        }
    } else if ((typeof obj != 'undefined') && (obj !== null) && (typeof obj === "object")){
        // for anything else but a scalar, we will use for-in-loop
        for (var i in obj){
            add(obj[i], i);
        }
    } else {
        uristrings.push(encodeURIComponent(temp) + '=' + encodeURIComponent(obj));
    }

    return uristrings.join(prefix)
                     .replace(/^&/, '')
                     .replace(/%20/g, '+'); 
};

//
//
// Uploader Classes
//
//

var qq = qq || {};
    
/**
 * Creates upload button, validates upload, but doesn't create file list or dd. 
 */
qq.FileUploaderBasic = function(o){
    this._options = {
        // set to true to see the server response
        debug: false,
        action: '/server/upload',
        params: {},
        button: null,
        multiple: true,
        maxConnections: 3,
        // validation        
        allowedExtensions: [],               
        sizeLimit: 0,   
        minSizeLimit: 0,                             
        // events
        // return false to cancel submit
        onSubmit: function(id, fileName){},
        onProgress: function(id, fileName, loaded, total){},
        onComplete: function(id, fileName, responseJSON, realFileName){},
        onCancel: function(id, fileName){},
        // messages                
        messages: {
            typeError: "{file} tiene una extension no válida. Solo extensiones {extensions}.",
            sizeError: "{file} es demasiado grande, el máximo tamaño de archivo es {sizeLimit}.",
            minSizeError: "{file} es demasiado chico, el minimo es de {minSizeLimit}.",
            emptyError: "{file} está vacio!, por favor, seleccione una imagen valida.",
            onLeave: "Los archivos están siendo subidos, si Ud. deja la pagina ahora, esto se cancelará."            
        },
        showMessage: function(message){
            alert(message);
        }               
    };
    qq.extend(this._options, o);
        
    // number of files being uploaded
    this._filesInProgress = 0;
    this._handler = this._createUploadHandler(); 
    
    if (this._options.button){ 
        this._button = this._createUploadButton(this._options.button);
    }
                        
    this._preventLeaveInProgress();         
};
   
qq.FileUploaderBasic.prototype = {
    setParams: function(params){
        this._options.params = params;
    },
    getInProgress: function(){
        return this._filesInProgress;         
    },
    _createUploadButton: function(element){
        var self = this;
        
        return new qq.UploadButton({
            element: element,
            multiple: this._options.multiple && qq.UploadHandlerXhr.isSupported(),
            onChange: function(input){
                self._onInputChange(input);
            }        
        });           
    },    
    _createUploadHandler: function(){
        var self = this,
            handlerClass;        
        
        if(qq.UploadHandlerXhr.isSupported()){           
            handlerClass = 'UploadHandlerXhr';                        
        } else {
            handlerClass = 'UploadHandlerForm';
        }

        var handler = new qq[handlerClass]({
            debug: this._options.debug,
            action: this._options.action,         
            maxConnections: this._options.maxConnections,   
            onProgress: function(id, fileName, loaded, total){                
                self._onProgress(id, fileName, loaded, total);
                self._options.onProgress(id, fileName, loaded, total);                    
            },            
            onComplete: function(id, fileName, result, realFileName){
                self._onComplete(id, fileName, result, realFileName);
                self._options.onComplete(id, fileName, result, realFileName);
            },
            onCancel: function(id, fileName){
                self._onCancel(id, fileName);
                self._options.onCancel(id, fileName);
            }
        });

        return handler;
    },    
    _preventLeaveInProgress: function(){
        var self = this;
        
        qq.attach(window, 'beforeunload', function(e){
            if (!self._filesInProgress){return;}
            
            var e = e || window.event;
            // for ie, ff
            e.returnValue = self._options.messages.onLeave;
            // for webkit
            return self._options.messages.onLeave;             
        });        
    },    
    _onSubmit: function(id, fileName){
        this._filesInProgress++;  
    },
    _onProgress: function(id, fileName, loaded, total){        
    },
    _onComplete: function(id, fileName, result, realFileName){
        this._filesInProgress--;                 
        if (result.error){
            this._options.showMessage(result.error);
        }             
    },
    _onCancel: function(id, fileName){
        this._filesInProgress--;        
    },
    _onInputChange: function(input){
        if (this._handler instanceof qq.UploadHandlerXhr){                
            this._uploadFileList(input.files);                   
        } else {             
            if (this._validateFile(input)){                
                this._uploadFile(input);                                    
            }                      
        }               
        this._button.reset();   
    },  
    _uploadFileList: function(files){
        for (var i=0; i this._options.sizeLimit){            
            this._error('sizeError', name);
            return false;
                        
        } else if (size && size < this._options.minSizeLimit){
            this._error('minSizeError', name);
            return false;            
        }
        
        return true;                
    },
    _error: function(code, fileName){
        var message = this._options.messages[code];        
        function r(name, replacement){ message = message.replace(name, replacement); }
        
        r('{file}', this._formatFileName(fileName));        
        r('{extensions}', this._options.allowedExtensions.join(', '));
        r('{sizeLimit}', this._formatSize(this._options.sizeLimit));
        r('{minSizeLimit}', this._formatSize(this._options.minSizeLimit));
        
        this._options.showMessage(message);                
    },
    _formatFileName: function(name){
        if (name.length > 33){
            name = name.slice(0, 19) + '...' + name.slice(-13);    
        }
        return name;
    },
    _isAllowedExtension: function(fileName){
        var ext = (-1 !== fileName.indexOf('.')) ? fileName.replace(/.*[.]/, '').toLowerCase() : '';
        var allowed = this._options.allowedExtensions;
        
        if (!allowed.length){return true;}        
        
        for (var i=0; i 99);
        
        return Math.max(bytes, 0.1).toFixed(1) + ['kB', 'MB', 'GB', 'TB', 'PB', 'EB'][i];          
    }
};
    
       
/**
 * Class that creates upload widget with drag-and-drop and file list
 * @inherits qq.FileUploaderBasic
 */
qq.FileUploader = function(o){
    // call parent constructor
    qq.FileUploaderBasic.apply(this, arguments);
    
    // additional options    
    qq.extend(this._options, {
        element: null,
        // if set, will be used instead of qq-upload-list in template
        listElement: null,
                
        template: '
' + 
                '
Arrastre los archivos hasta aquí para subirlos
' +
                '
Clic para subir archivos
' +
                '
' + 
             '
',

        // template for one item in file list
        fileTemplate: '
' +
                '' +
                '' +
                '' +
                'Cancelar' +
                '' +
            '
',        
        
        classes: {
            // used to get elements from templates
            button: 'qq-upload-button',
            drop: 'qq-upload-drop-area',
            dropActive: 'qq-upload-drop-area-active',
            list: 'qq-upload-list',
                        
            file: 'qq-upload-file',
            spinner: 'qq-upload-spinner',
            size: 'qq-upload-size',
            cancel: 'qq-upload-cancel',

            // added to list item when upload completes
            // used in css to hide progress spinner
            success: 'qq-upload-success',
            fail: 'qq-upload-fail'
        }
    });
    // overwrite options with user supplied    
    qq.extend(this._options, o);       

    this._element = this._options.element;
    this._element.innerHTML = this._options.template;        
    this._listElement = this._options.listElement || this._find(this._element, 'list');
    
    this._classes = this._options.classes;
        
    this._button = this._createUploadButton(this._find(this._element, 'button'));        
    
    this._bindCancelEvent();
    this._setupDragDrop();
};

// inherit from Basic Uploader
qq.extend(qq.FileUploader.prototype, qq.FileUploaderBasic.prototype);

qq.extend(qq.FileUploader.prototype, {
    /**
     * Gets one of the elements listed in this._options.classes
     **/
    _find: function(parent, type){                                
        var element = qq.getByClass(parent, this._options.classes[type])[0];        
        if (!element){
            throw new Error('element not found ' + type);
        }
        
        return element;
    },
    _setupDragDrop: function(){
        var self = this,
            dropArea = this._find(this._element, 'drop');                        

        var dz = new qq.UploadDropZone({
            element: dropArea,
            onEnter: function(e){
                qq.addClass(dropArea, self._classes.dropActive);
                e.stopPropagation();
            },
            onLeave: function(e){
                e.stopPropagation();
            },
            onLeaveNotDescendants: function(e){
                qq.removeClass(dropArea, self._classes.dropActive);  
            },
            onDrop: function(e){
                dropArea.style.display = 'none';
                qq.removeClass(dropArea, self._classes.dropActive);
                self._uploadFileList(e.dataTransfer.files);    
            }
        });
                
        dropArea.style.display = 'none';

        qq.attach(document, 'dragenter', function(e){     
            if (!dz._isValidFileDrag(e)) return; 
            
            dropArea.style.display = 'block';            
        });                 
        qq.attach(document, 'dragleave', function(e){
            if (!dz._isValidFileDrag(e)) return;            
            
            var relatedTarget = document.elementFromPoint(e.clientX, e.clientY);
            // only fire when leaving document out
            if ( ! relatedTarget || relatedTarget.nodeName == "HTML"){               
                dropArea.style.display = 'none';                                            
            }
        });                
    },
    _onSubmit: function(id, fileName){
        qq.FileUploaderBasic.prototype._onSubmit.apply(this, arguments);
        this._addToList(id, fileName);  
    },
    _onProgress: function(id, fileName, loaded, total){
        qq.FileUploaderBasic.prototype._onProgress.apply(this, arguments);

        var item = this._getItemByFileId(id);
        var size = this._find(item, 'size');
        size.style.display = 'inline';
        
        var text; 
        if (loaded != total){
            text = Math.round(loaded / total * 100) + '% de ' + this._formatSize(total);
        } else {                                   
            text = this._formatSize(total);
        }          
        
        qq.setText(size, text);         
    },
    _onComplete: function(id, fileName, result, realFileName){
        qq.FileUploaderBasic.prototype._onComplete.apply(this, arguments);

        // mark completed
        var item = this._getItemByFileId(id);                
        qq.remove(this._find(item, 'cancel'));
        qq.remove(this._find(item, 'spinner'));
        
        if (result.success){
            qq.addClass(item, this._classes.success);
        } else {
            qq.addClass(item, this._classes.fail);
        }         
    },
    _addToList: function(id, fileName){
        var item = qq.toElement(this._options.fileTemplate);                
        item.qqFileId = id;

        var fileElement = this._find(item, 'file');        
        qq.setText(fileElement, this._formatFileName(fileName));
        this._find(item, 'size').style.display = 'none';        

        this._listElement.appendChild(item);
    },
    _getItemByFileId: function(id){
        var item = this._listElement.firstChild;        
        
        // there can't be txt nodes in dynamically created list
        // and we can  use nextSibling
        while (item){            
            if (item.qqFileId == id) return item;            
            item = item.nextSibling;
        }          
    },
    /**
     * delegate click event for cancel link 
     **/
    _bindCancelEvent: function(){
        var self = this,
            list = this._listElement;            
        
        qq.attach(list, 'click', function(e){            
            e = e || window.event;
            var target = e.target || e.srcElement;
            
            if (qq.hasClass(target, self._classes.cancel)){                
                qq.preventDefault(e);
               
                var item = target.parentNode;
                self._handler.cancel(item.qqFileId);
                qq.remove(item);
            }
        });
    }    
});
    
qq.UploadDropZone = function(o){
    this._options = {
        element: null,  
        onEnter: function(e){},
        onLeave: function(e){},  
        // is not fired when leaving element by hovering descendants   
        onLeaveNotDescendants: function(e){},   
        onDrop: function(e){}                       
    };
    qq.extend(this._options, o); 
    
    this._element = this._options.element;
    
    this._disableDropOutside();
    this._attachEvents();   
};

qq.UploadDropZone.prototype = {
    _disableDropOutside: function(e){
        // run only once for all instances
        if (!qq.UploadDropZone.dropOutsideDisabled ){

            qq.attach(document, 'dragover', function(e){
                if (e.dataTransfer){
                    e.dataTransfer.dropEffect = 'none';
                    e.preventDefault(); 
                }           
            });
            
            qq.UploadDropZone.dropOutsideDisabled = true; 
        }        
    },
    _attachEvents: function(){
        var self = this;              
                  
        qq.attach(self._element, 'dragover', function(e){
            if (!self._isValidFileDrag(e)) return;
            
            var effect = e.dataTransfer.effectAllowed;
            if (effect == 'move' || effect == 'linkMove'){
                e.dataTransfer.dropEffect = 'move'; // for FF (only move allowed)    
            } else {                    
                e.dataTransfer.dropEffect = 'copy'; // for Chrome
            }
                                                     
            e.stopPropagation();
            e.preventDefault();                                                                    
        });
        
        qq.attach(self._element, 'dragenter', function(e){
            if (!self._isValidFileDrag(e)) return;
                        
            self._options.onEnter(e);
        });
        
        qq.attach(self._element, 'dragleave', function(e){
            if (!self._isValidFileDrag(e)) return;
            
            self._options.onLeave(e);
            
            var relatedTarget = document.elementFromPoint(e.clientX, e.clientY);                      
            // do not fire when moving a mouse over a descendant
            if (qq.contains(this, relatedTarget)) return;
                        
            self._options.onLeaveNotDescendants(e); 
        });
                
        qq.attach(self._element, 'drop', function(e){
            if (!self._isValidFileDrag(e)) return;
            
            e.preventDefault();
            self._options.onDrop(e);
        });          
    },
    _isValidFileDrag: function(e){
        var dt = e.dataTransfer,
            // do not check dt.types.contains in webkit, because it crashes safari 4            
            isWebkit = navigator.userAgent.indexOf("AppleWebKit") > -1;                        

        // dt.effectAllowed is none in Safari 5
        // dt.types.contains check is for firefox            
        return dt && dt.effectAllowed != 'none' && 
            (dt.files || (!isWebkit && dt.types.contains && dt.types.contains('Files')));
        
    }        
}; 

qq.UploadButton = function(o){
    this._options = {
        element: null,  
        // if set to true adds multiple attribute to file input      
        multiple: false,
        // name attribute of file input
        name: 'file',
        onChange: function(input){},
        hoverClass: 'qq-upload-button-hover',
        focusClass: 'qq-upload-button-focus'                       
    };
    
    qq.extend(this._options, o);
        
    this._element = this._options.element;
    
    // make button suitable container for input
    qq.css(this._element, {
        position: 'relative',
        overflow: 'hidden',
        // Make sure browse button is in the right side
        // in Internet Explorer
        direction: 'ltr'
    });   
    
    this._input = this._createInput();
};

qq.UploadButton.prototype = {
    /* returns file input element */    
    getInput: function(){
        return this._input;
    },
    /* cleans/recreates the file input */
    reset: function(){
        if (this._input.parentNode){
            qq.remove(this._input);    
        }                
        
        qq.removeClass(this._element, this._options.focusClass);
        this._input = this._createInput();
    },    
    _createInput: function(){                
        var input = document.createElement("input");
        
        if (this._options.multiple){
            input.setAttribute("multiple", "multiple");
        }
                
        input.setAttribute("type", "file");
        input.setAttribute("name", this._options.name);
        
        qq.css(input, {
            position: 'absolute',
            // in Opera only 'browse' button
            // is clickable and it is located at
            // the right side of the input
            right: 0,
            top: 0,
            fontFamily: 'Arial',
            // 4 persons reported this, the max values that worked for them were 243, 236, 236, 118
            fontSize: '118px',
            margin: 0,
            padding: 0,
            cursor: 'pointer',
            opacity: 0
        });
        
        this._element.appendChild(input);

        var self = this;
        qq.attach(input, 'change', function(){
            self._options.onChange(input);
        });
                
        qq.attach(input, 'mouseover', function(){
            qq.addClass(self._element, self._options.hoverClass);
        });
        qq.attach(input, 'mouseout', function(){
            qq.removeClass(self._element, self._options.hoverClass);
        });
        qq.attach(input, 'focus', function(){
            qq.addClass(self._element, self._options.focusClass);
        });
        qq.attach(input, 'blur', function(){
            qq.removeClass(self._element, self._options.focusClass);
        });

        // IE and Opera, unfortunately have 2 tab stops on file input
        // which is unacceptable in our case, disable keyboard access
        if (window.attachEvent){
            // it is IE or Opera
            input.setAttribute('tabIndex', "-1");
        }

        return input;            
    }        
};

/**
 * Class for uploading files, uploading itself is handled by child classes
 */
qq.UploadHandlerAbstract = function(o){
    this._options = {
        debug: false,
        action: '/upload.php',
        // maximum number of concurrent uploads        
        maxConnections: 999,
        onProgress: function(id, fileName, loaded, total){},
        onComplete: function(id, fileName, response, realFileName){},
        onCancel: function(id, fileName){}
    };
    qq.extend(this._options, o);    
    
    this._queue = [];
    // params for files in queue
    this._params = [];
};
qq.UploadHandlerAbstract.prototype = {
    log: function(str){
        if (this._options.debug && window.console) console.log('[uploader] ' + str);        
    },
    /**
     * Adds file or file input to the queue
     * @returns id
     **/    
    add: function(file){},
    /**
     * Sends the file identified by id and additional query params to the server
     */
    upload: function(id, params){
        var len = this._queue.push(id);

        var copy = {};        
        qq.extend(copy, params);
        this._params[id] = copy;        
                
        // if too many active uploads, wait...
        if (len <= this._options.maxConnections){               
            this._upload(id, this._params[id]);
        }
    },
    /**
     * Cancels file upload by id
     */
    cancel: function(id){
        this._cancel(id);
        this._dequeue(id);
    },
    /**
     * Cancells all uploads
     */
    cancelAll: function(){
        for (var i=0; i= max){
            var nextId = this._queue[max-1];
            this._upload(nextId, this._params[nextId]);
        }
    }        
};

/**
 * Class for uploading files using form and iframe
 * @inherits qq.UploadHandlerAbstract
 */
qq.UploadHandlerForm = function(o){
    qq.UploadHandlerAbstract.apply(this, arguments);
       
    this._inputs = {};
};
// @inherits qq.UploadHandlerAbstract
qq.extend(qq.UploadHandlerForm.prototype, qq.UploadHandlerAbstract.prototype);

qq.extend(qq.UploadHandlerForm.prototype, {
    add: function(fileInput){
        fileInput.setAttribute('name', 'qqfile');
        var id = 'qq-upload-handler-iframe' + qq.getUniqueId();       
        
        this._inputs[id] = fileInput;
        
        // remove file input from DOM
        if (fileInput.parentNode){
            qq.remove(fileInput);
        }
                
        return id;
    },
    getName: function(id){
        // get input value and remove path to normalize
        return this._inputs[id].value.replace(/.*(\/|\\)/, "");
    },    
    _cancel: function(id){
        this._options.onCancel(id, this.getName(id));
        
        delete this._inputs[id];        

        var iframe = document.getElementById(id);
        if (iframe){
            // to cancel request set src to something else
            // we use src="javascript:false;" because it doesn't
            // trigger ie6 prompt on https
            iframe.setAttribute('src', 'javascript:false;');

            qq.remove(iframe);
        }
    },     
    _upload: function(id, params){                        
        var input = this._inputs[id];
        
        if (!input){
            throw new Error('file with passed id was not added, or already uploaded or cancelled');
        }                

        var fileName = this.getName(id);
                
        var iframe = this._createIframe(id);
        var form = this._createForm(iframe, params);
        form.appendChild(input);

        var self = this;
        this._attachLoadEvent(iframe, function(){                                 
            self.log('iframe loaded');
            
            var response = self._getIframeContentJSON(iframe);

            self._options.onComplete(id, fileName, response);
            self._dequeue(id);
            
            delete self._inputs[id];
            // timeout added to fix busy state in FF3.6
            setTimeout(function(){
                qq.remove(iframe);
            }, 1);
        });

        form.submit();        
        qq.remove(form);        
        
        return id;
    }, 
    _attachLoadEvent: function(iframe, callback){
        qq.attach(iframe, 'load', function(){
            // when we remove iframe from dom
            // the request stops, but in IE load
            // event fires
            if (!iframe.parentNode){
                return;
            }

            // fixing Opera 10.53
            if (iframe.contentDocument &&
                iframe.contentDocument.body &&
                iframe.contentDocument.body.innerHTML == "false"){
                // In Opera event is fired second time
                // when body.innerHTML changed from false
                // to server response approx. after 1 sec
                // when we upload file with iframe
                return;
            }

            callback();
        });
    },
    /**
     * Returns json object received by iframe from server.
     */
    _getIframeContentJSON: function(iframe){
        // iframe.contentWindow.document - for IE<7
        var doc = iframe.contentDocument ? iframe.contentDocument: iframe.contentWindow.document,
            response;
        
        this.log("converting iframe's innerHTML to JSON");
        this.log("innerHTML = " + doc.body.innerHTML);
                        
        try {
            response = eval("(" + doc.body.innerHTML + ")");
        } catch(err){
            response = {};
        }        

        return response;
    },
    /**
     * Creates iframe with unique name
     */
    _createIframe: function(id){
        // We can't use following code as the name attribute
        // won't be properly registered in IE6, and new window
        // on form submit will open
        // var iframe = document.createElement('iframe');
        // iframe.setAttribute('name', id);

        var iframe = qq.toElement('