// Use the following config variable to set modified optional settings copied from config-defaults.php
    'config'=>array(
    // debug: Set this to 1 if you are looking for errors. If you still get no errors after enabling this
    // then please check your error-logs - either in your hosting provider admin panel or in some /logs directory
    // on your webspace.
    // LimeSurvey developers: Set this to 2 to additionally display STRICT PHP error messages and get full access to standard templates
        'debug'=>0,
        'debugsql'=>0, // Set this to 1 to enanble sql logging, only active when debug = 2
 

Put the code here

 
133      */
134     public function __get($name)
135     {
136         if(isset($this->_attributes[$name]))
137             return $this->_attributes[$name];
138         elseif(isset($this->getMetaData()->columns[$name]))
139             return null;
140         elseif(isset($this->_related[$name]))
141             return $this->_related[$name];
142         elseif(isset($this->getMetaData()->relations[$name]))
143             return $this->getRelated($name);
144         else
145             return parent::__get($name);
146     }
147 
148     /**
149      * PHP setter magic method.
150      * This method is overridden so that AR attributes can be accessed like properties.
151      * @param string $name property name
152      * @param mixed $value property value
153      * @throws CException
154      */
155     public function __set($name,$value)
156     {
157         if($this->setAttribute($name,$value)===false)

163      * @return string existing $sTemplateName
164      * @throws Exception
165      */
166     public static function templateNameFilter($sTemplateName)
167     {
168         $sTemplateName = sanitize_filename($sTemplateName, false, false, false, true);
169 
170         // If the names has already been filtered, we skip the process
171         if (!empty(self::$aNamesFiltered[$sTemplateName])) {
172             return self::$aNamesFiltered[$sTemplateName];
173         }

#3   
+
 /var/www/html/limesurvey/vendor/yiisoft/yii/framework/base/CComponent.php(111): TemplateConfiguration->getPreview()
#4   
+
 /var/www/html/limesurvey/vendor/yiisoft/yii/framework/db/ar/CActiveRecord.php(145): CComponent->__get()
#5   
+
 /var/www/html/limesurvey/application/models/TemplateConfiguration.php(1477): CActiveRecord->__get()
#6   
+
 /var/www/html/limesurvey/application/models/Template.php(507): TemplateConfiguration->__get()
#7   
+
 /var/www/html/limesurvey/application/extensions/admin/survey/ListSurveysWidget/views/massive_actions/_select_survey_theme.php(13): Template::getTemplateListWithPreviews()
#8   
+
 /var/www/html/limesurvey/vendor/yiisoft/yii/framework/web/CBaseController.php(126): require("/var/www/html/limesurvey/application/extensions/admin/survey/Lis...")
#9   
+
 /var/www/html/limesurvey/vendor/yiisoft/yii/framework/web/CBaseController.php(95): CBaseController->renderInternal()
#10   
+
 /var/www/html/limesurvey/application/extensions/admin/survey/ListSurveysWidget/views/massive_actions/_selector.php(61): CBaseController->renderFile()
#11   
+
 /var/www/html/limesurvey/vendor/yiisoft/yii/framework/web/CBaseController.php(126): require("/var/www/html/limesurvey/application/extensions/admin/survey/Lis...")
#12   
+
 /var/www/html/limesurvey/vendor/yiisoft/yii/framework/web/CBaseController.php(95): CBaseController->renderInternal()
#13   
+
 /var/www/html/limesurvey/vendor/yiisoft/yii/framework/web/widgets/CWidget.php(244): CBaseController->renderFile()
#14   
+
 /var/www/html/limesurvey/application/extensions/admin/survey/ListSurveysWidget/ListSurveysWidget.php(60): CWidget->render()
#15   
+
 /var/www/html/limesurvey/vendor/yiisoft/yii/framework/web/CBaseController.php(182): ListSurveysWidget->run()
#16   
+
 /var/www/html/limesurvey/application/views/admin/super/welcome.php(198): CBaseController->widget()
#17   
+
 /var/www/html/limesurvey/vendor/yiisoft/yii/framework/web/CBaseController.php(126): require("/var/www/html/limesurvey/application/views/admin/super/welcome.p...")
#18   
+
 /var/www/html/limesurvey/vendor/yiisoft/yii/framework/web/CBaseController.php(95): CBaseController->renderInternal()
#19   
+
 /var/www/html/limesurvey/vendor/yiisoft/yii/framework/web/CController.php(872): CBaseController->renderFile()
#20   
+
 /var/www/html/limesurvey/application/controllers/AdminController.php(261): CController->renderPartial()
#21   
+
 /var/www/html/limesurvey/application/core/SurveyCommonAction.php(273): AdminController->renderPartial()
#22   
+
 /var/www/html/limesurvey/application/core/SurveyCommonAction.php(395): SurveyCommonAction->renderCentralContents()
#23   
+
 /var/www/html/limesurvey/application/controllers/admin/index.php(94): SurveyCommonAction->renderWrappedTemplate()
#24   
 unknown(0): Index->run()
#25   
+
 /var/www/html/limesurvey/vendor/yiisoft/yii/framework/web/actions/CAction.php(115): ReflectionMethod->invokeArgs()
#26   
+
 /var/www/html/limesurvey/application/core/SurveyCommonAction.php(83): CAction->runWithParamsInternal()
#27   
+
 /var/www/html/limesurvey/vendor/yiisoft/yii/framework/web/CController.php(308): SurveyCommonAction->runWithParams()
#28   
+
 /var/www/html/limesurvey/vendor/yiisoft/yii/framework/web/CController.php(286): CController->runAction()
#29   
+
 /var/www/html/limesurvey/vendor/yiisoft/yii/framework/web/CController.php(265): CController->runActionWithFilters()
#30   
+
 /var/www/html/limesurvey/application/controllers/AdminController.php(202): CController->run()
#31   
+
 /var/www/html/limesurvey/vendor/yiisoft/yii/framework/web/CWebApplication.php(282): AdminController->run()
#32   
+
 /var/www/html/limesurvey/vendor/yiisoft/yii/framework/web/CWebApplication.php(141): CWebApplication->runController()
#33   
+
 /var/www/html/limesurvey/vendor/yiisoft/yii/framework/base/CApplication.php(185): CWebApplication->processRequest()
#34   
+
 /var/www/html/limesurvey/index.php(161): CApplication->run() 

apt install php-mbstring