CForm

public function __construct($config,$model=null,$parent=null)
{
    $this->setModel($model);
    if($parent===null)
        $parent=Yii::app()->getController();
    parent::__construct($config,$parent);
    $this->init();
}

public function addedElement($name,$element,$forButtons)
{
}

public function clicked($name)
{
    if(strcasecmp($this->getRoot()->method,'get'))
        return isset($_POST[$name]);
    else
        return isset($_GET[$name]);
}

protected function evaluateVisible()
{
    foreach($this->getElements() as $element)
        if($element->getVisible())
            return true;
    return false;
}

public function getActiveFormWidget()
{
    if($this->_activeForm!==null)
        return $this->_activeForm;
    else
        return $this->getRoot()->_activeForm;
}

public function getButtons()
{
    if($this->_buttons===null)
        $this->_buttons=new CFormElementCollection($this,true);
    return $this->_buttons;
}

public function getElements()
{
    if($this->_elements===null)
        $this->_elements=new CFormElementCollection($this,false);
    return $this->_elements;
}

public function getModel($checkParent=true)
{
    if(!$checkParent)
        return $this->_model;
    $form=$this;
    while($form->_model===null && $form->getParent() instanceof self)
        $form=$form->getParent();
    return $form->_model;
}

public function getModels()
{
    $models=array();
    if($this->_model!==null)
        $models[]=$this->_model;
    foreach($this->getElements() as $element)
    {
        if($element instanceof self)
            $models=array_merge($models,$element->getModels());
    }
    return $models;
}

public function getOwner()
{
    $owner=$this->getParent();
    while($owner instanceof self)
        $owner=$owner->getParent();
    return $owner;
}

public function getRoot()
{
    $root=$this;
    while($root->getParent() instanceof self)
        $root=$root->getParent();
    return $root;
}

protected function getUniqueId()
{
    if(isset($this->attributes['id']))
        return 'yform_'.$this->attributes['id'];
    else
        return 'yform_'.sprintf('%x',crc32(serialize(array_keys($this->getElements()->toArray()))));
}

protected function init()
{
}

public function loadData()
{
    if($this->_model!==null)
    {
        $class=get_class($this->_model);
        if(strcasecmp($this->getRoot()->method,'get'))
        {
            if(isset($_POST[$class]))
                $this->_model->setAttributes($_POST[$class]);
        }
        else if(isset($_GET[$class]))
            $this->_model->setAttributes($_GET[$class]);
    }
    foreach($this->getElements() as $element)
    {
        if($element instanceof self)
            $element->loadData();
    }
}

public function offsetExists($offset)
{
    return $this->getElements()->contains($offset);
}

public function offsetGet($offset)
{
    return $this->getElements()->itemAt($offset);
}

public function offsetSet($offset,$item)
{
    $this->getElements()->add($offset,$item);
}

public function offsetUnset($offset)
{
    $this->getElements()->remove($offset);
}

public function removedElement($name,$element,$forButtons)
{
}

public function render()
{
    return $this->renderBegin() . $this->renderBody() . $this->renderEnd();
}

public function renderBegin()
{
    if($this->getParent() instanceof self)
        return '';
    else
    {
        $options=$this->activeForm;
        if(isset($options['class']))
        {
            $class=$options['class'];
            unset($options['class']);
        }
        else
            $class='CActiveForm';
        $options['action']=$this->action;
        $options['method']=$this->method;
        if(isset($options['htmlOptions']))
        {
            foreach($this->attributes as $name=>$value)
                $options['htmlOptions'][$name]=$value;
        }
        else
            $options['htmlOptions']=$this->attributes;
        ob_start();
        $this->_activeForm=$this->getOwner()->beginWidget($class, $options);
        return ob_get_clean() . "<div style=\"visibility:hidden\">".CHtml::hiddenField($this->getUniqueID(),1)."</div>\n";
    }
}

public function renderBody()
{
    $output='';
    if($this->title!==null)
    {
        if($this->getParent() instanceof self)
        {
            $attributes=$this->attributes;
            unset($attributes['name'],$attributes['type']);
            $output=CHtml::openTag('fieldset', $attributes)."<legend>".$this->title."</legend>\n";
        }
        else
            $output="<fieldset>\n<legend>".$this->title."</legend>\n";
    }

    if($this->description!==null)
        $output.="<div class=\"description\">\n".$this->description."</div>\n";

    if($this->showErrorSummary && ($model=$this->getModel(false))!==null)
        $output.=$this->getActiveFormWidget()->errorSummary($model)."\n";

    $output.=$this->renderElements()."\n".$this->renderButtons()."\n";

    if($this->title!==null)
        $output.="</fieldset>\n";

    return $output;
}

public function renderButtons()
{
    $output='';
    foreach($this->getButtons() as $button)
        $output.=$this->renderElement($button);
    return $output!=='' ? "<div class=\"row buttons\">".$output."</div>\n" : '';
}

public function renderElement($element)
{
    if(is_string($element))
    {
        if(($e=$this[$element])===null && ($e=$this->getButtons()->itemAt($element))===null)
            return $element;
        else
            $element=$e;
    }
    if($element->getVisible())
    {
        if($element instanceof CFormInputElement)
        {
            if($element->type==='hidden')
                return "<div style=\"visibility:hidden\">\n".$element->render()."</div>\n";
            else
                return "<div class=\"row field_{$element->name}\">\n".$element->render()."</div>\n";
        }
        else if($element instanceof CFormButtonElement)
            return $element->render()."\n";
        else
            return $element->render();
    }
    return '';
}

public function renderElements()
{
    $output='';
    foreach($this->getElements() as $element)
        $output.=$this->renderElement($element);
    return $output;
}

public function renderEnd()
{
    if($this->getParent() instanceof self)
        return '';
    else
    {
        ob_start();
        $this->getOwner()->endWidget();
        return ob_get_clean();
    }
}

public function setButtons($buttons)
{
    $collection=$this->getButtons();
    foreach($buttons as $name=>$config)
        $collection->add($name,$config);
}

public function setElements($elements)
{
    $collection=$this->getElements();
    foreach($elements as $name=>$config)
        $collection->add($name,$config);
}

public function setModel($model)
{
    $this->_model=$model;
}

public function submitted($buttonName='submit',$loadData=true)
{
    $ret=$this->clicked($this->getUniqueId()) && $this->clicked($buttonName);
    if($ret && $loadData)
        $this->loadData();
    return $ret;
}

public function validate()
{
    $ret=true;
    foreach($this->getModels() as $model)
        $ret=$model->validate() && $ret;
    return $ret;
}