未定义的变量是否在不同的PHP版本之间存在问题？

function get_cal_eventTitle($year, $month){
        $this->db->where(\'eventYear =\', $year);
        $this->db->where(\'eventMonth =\', $month);
        $this->db->select(\'eventTitle\');
            $query = $this->db->get(\'tb_event_calendar\');

        $result = $query->result(); 

        foreach ($result as $row)
        {
            $withEmptyTitle = $row->eventTitle;         
            //echo $withEmptyTitle.\'<br>\';
            $noEmptyTitle = str_replace(\" \",\"%20\",$withEmptyTitle);
            $withUrlTitle = \'<a href=\'.base_url().\'index.php/calendar/singleEvent/\'.$year.\'/\'.$month.\'/\'.$noEmptyTitle.\'/\'.\'>\'.$withEmptyTitle.\'</a>\';         
            //echo $withUrlTitle.\'<br>\';
            $row->eventTitle = $withUrlTitle;          
        }
        return $result;
    }

A PHP Error was encountered
Severity: Notice

Message: Undefined variable: withUrlTitle

Filename: models/calendar_model.php

Line Number: 54 // $withEmptyTitle = $row->eventTitle;  

withEmptyTitle