HTMLPurifier_AttrDef_Enum::validate PHP Method

    public function validate($string, $config, $context)
    {
        $string = trim($string);
        if (!$this->case_sensitive) {
            // we may want to do full case-insensitive libraries
            $string = ctype_lower($string) ? $string : strtolower($string);
        }
        $result = isset($this->valid_values[$string]);
        return $result ? $string : false;
    }

 public function validate($string, $config, $context)
 {
     if ($this->valid_values === false) {
         $this->valid_values = $config->get('Attr', 'AllowedFrameTargets');
     }
     return parent::validate($string, $config, $context);
 }