CStringValidator

public function clientValidateAttribute($object,$attribute)
{
    $label=$object->getAttributeLabel($attribute);

    if(($message=$this->message)===null)
        $message=Yii::t('yii','{attribute} is of the wrong length (should be {length} characters).');
    $message=strtr($message, array(
        '{attribute}'=>$label,
        '{length}'=>$this->is,
    ));

    if(($tooShort=$this->tooShort)===null)
        $tooShort=Yii::t('yii','{attribute} is too short (minimum is {min} characters).');
    $tooShort=strtr($tooShort, array(
        '{attribute}'=>$label,
        '{min}'=>$this->min,
    ));

    if(($tooLong=$this->tooLong)===null)
        $tooLong=Yii::t('yii','{attribute} is too long (maximum is {max} characters).');
    $tooLong=strtr($tooLong, array(
        '{attribute}'=>$label,
        '{max}'=>$this->max,
    ));

    $js='';
    if($this->min!==null)
    {
        $js.="
if(value.length<{$this->min}) {
messages.push(".CJSON::encode($tooShort).");
}
";
    }
    if($this->max!==null)
    {
        $js.="
if(value.length>{$this->max}) {
messages.push(".CJSON::encode($tooLong).");
}
";
    }
    if($this->is!==null)
    {
        $js.="
if(value.length!={$this->is}) {
messages.push(".CJSON::encode($message).");
}
";
    }

    if($this->allowEmpty)
    {
        $js="
if(jQuery.trim(value)!='') {
$js
}
";
    }

    return $js;
}

protected function validateAttribute($object,$attribute)
{
    $value=$object->$attribute;
    if($this->allowEmpty && $this->isEmpty($value))
        return;

    if(is_array($value))
    {
        // https://github.com/yiisoft/yii/issues/1955
        $this->addError($object,$attribute,Yii::t('yii','{attribute} is invalid.'));
        return;
    }

    if(function_exists('mb_strlen') && $this->encoding!==false)
        $length=mb_strlen($value, $this->encoding ? $this->encoding : Yii::app()->charset);
    else
        $length=strlen($value);

    if($this->min!==null && $length<$this->min)
    {
        $message=$this->tooShort!==null?$this->tooShort:Yii::t('yii','{attribute} is too short (minimum is {min} characters).');
        $this->addError($object,$attribute,$message,array('{min}'=>$this->min));
    }
    if($this->max!==null && $length>$this->max)
    {
        $message=$this->tooLong!==null?$this->tooLong:Yii::t('yii','{attribute} is too long (maximum is {max} characters).');
        $this->addError($object,$attribute,$message,array('{max}'=>$this->max));
    }
    if($this->is!==null && $length!==$this->is)
    {
        $message=$this->message!==null?$this->message:Yii::t('yii','{attribute} is of the wrong length (should be {length} characters).');
        $this->addError($object,$attribute,$message,array('{length}'=>$this->is));
    }
}