CCompareValidator

public function clientValidateAttribute($object,$attribute)
{
    if($this->compareValue !== null)
    {
        $compareTo=$this->compareValue;
        $compareValue=CJSON::encode($this->compareValue);
    }
    else
    {
        $compareAttribute=$this->compareAttribute === null ? $attribute . '_repeat' : $this->compareAttribute;
        $compareValue="jQuery('#" . (CHtml::activeId($object, $compareAttribute)) . "').val()";
        $compareTo=$object->getAttributeLabel($compareAttribute);
    }

    $message=$this->message;
    switch($this->operator)
    {
        case '=':
        case '==':
            if($message===null)
                $message=Yii::t('yii','{attribute} must be repeated exactly.');
            $condition='value!='.$compareValue;
            break;
        case '!=':
            if($message===null)
                $message=Yii::t('yii','{attribute} must not be equal to "{compareValue}".');
            $condition='value=='.$compareValue;
            break;
        case '>':
            if($message===null)
                $message=Yii::t('yii','{attribute} must be greater than "{compareValue}".');
            $condition='parseFloat(value)<=parseFloat('.$compareValue.')';
            break;
        case '>=':
            if($message===null)
                $message=Yii::t('yii','{attribute} must be greater than or equal to "{compareValue}".');
            $condition='parseFloat(value)<parseFloat('.$compareValue.')';
            break;
        case '<':
            if($message===null)
                $message=Yii::t('yii','{attribute} must be less than "{compareValue}".');
            $condition='parseFloat(value)>=parseFloat('.$compareValue.')';
            break;
        case '<=':
            if($message===null)
                $message=Yii::t('yii','{attribute} must be less than or equal to "{compareValue}".');
            $condition='parseFloat(value)>parseFloat('.$compareValue.')';
            break;
        default:
            throw new CException(Yii::t('yii','Invalid operator "{operator}".',array('{operator}'=>$this->operator)));
    }

    $message=strtr($message,array(
        '{attribute}'=>$object->getAttributeLabel($attribute),
        '{compareAttribute}'=>$compareTo,
    ));

    return "
if(".($this->allowEmpty ? "jQuery.trim(value)!='' && " : '').$condition.") {
messages.push(".CJSON::encode($message).".replace('{compareValue}', ".$compareValue."));
}
";
}

protected function validateAttribute($object,$attribute)
{
    $value=$object->$attribute;
    if($this->allowEmpty && $this->isEmpty($value))
        return;
    if($this->compareValue!==null)
        $compareTo=$compareValue=$this->compareValue;
    else
    {
        $compareAttribute=$this->compareAttribute===null ? $attribute.'_repeat' : $this->compareAttribute;
        $compareValue=$object->$compareAttribute;
        $compareTo=$object->getAttributeLabel($compareAttribute);
    }

    switch($this->operator)
    {
        case '=':
        case '==':
            if(($this->strict && $value!==$compareValue) || (!$this->strict && $value!=$compareValue))
                $message=$this->message!==null?$this->message:Yii::t('yii','{attribute} must be repeated exactly.');
            break;
        case '!=':
            if(($this->strict && $value===$compareValue) || (!$this->strict && $value==$compareValue))
                $message=$this->message!==null?$this->message:Yii::t('yii','{attribute} must not be equal to "{compareValue}".');
            break;
        case '>':
            if($value<=$compareValue)
                $message=$this->message!==null?$this->message:Yii::t('yii','{attribute} must be greater than "{compareValue}".');
            break;
        case '>=':
            if($value<$compareValue)
                $message=$this->message!==null?$this->message:Yii::t('yii','{attribute} must be greater than or equal to "{compareValue}".');
            break;
        case '<':
            if($value>=$compareValue)
                $message=$this->message!==null?$this->message:Yii::t('yii','{attribute} must be less than "{compareValue}".');
            break;
        case '<=':
            if($value>$compareValue)
                $message=$this->message!==null?$this->message:Yii::t('yii','{attribute} must be less than or equal to "{compareValue}".');
            break;
        default:
            throw new CException(Yii::t('yii','Invalid operator "{operator}".',array('{operator}'=>$this->operator)));
    }
    if(!empty($message))
        $this->addError($object,$attribute,$message,array('{compareAttribute}'=>$compareTo,'{compareValue}'=>$compareValue));
}