间接修改重载属性Fbevent :: $ location无效

Question

我正在尝试将字符串推入对象中。此错误在以下行引发：

$event->location[0]->image = $mapLocation->image;

在这个函数中：

public static function assignMarkers($events)
    {
        // Initialise pageIds array and counter
        $pageIds = [];
        $locations = [];
        $locationsCounter = 0;

        // Loop events and place unique pages in pageId array
        foreach($events as $event)
        {
            if ( ! in_array($event->location[0]->pageId, $pageIds))
            {
                array_push($pageIds, $event->location[0]->pageId);

                // Construct mapLocation object
                $mapLocation = new stdClass();
                $mapLocation->latitude = $event->location[0]->latitude;
                $mapLocation->longitude = $event->location[0]->longitude;
                $mapLocation->pageId = $event->location[0]->pageId;
                $mapLocation->image = 'assets/img/markers' . $locationsCounter . '.png';

                $locationsCounter++;
                array_push($locations, $mapLocation);

                // Push image back to event
                $event->location[0]->image = $mapLocation->image;

            } else {
                // it's already in the array
                // set the events image to the one in the corresponding location array position
                foreach($locations as $location)
                {
                    if ($event->location[0]->pageId == $location->pageId) {
                        // We have a match
                        $event->location->image = $location->image;
                    }
                }
            }
        }

        return $events;
    }

$ events是一个Eloquent Collection（使用Laravel）。我不确定这个错误意味着什么 - 有人可以帮忙吗？