类型：错误消息：字符串不支持[]运算符

I'm getting information from database, saving it in array and echoing it in a form with loop structure and I'm having problems when I try to save the modified information to database.

I'm getting this error:

message: [] operator not supported for string

$this->db->select('*');
        $this->db->from('tbl_memory_questions');
        $this->db->order_by('rand()');
        $this->db->limit(1);
        $GetWordsFromdb = $this->db->where('memQuesType', 'Words');
        $GetWord = $GetWordsFromdb->get(); print_r($GetWord->result());exit;
        $GetWords = array();
        $MemQuesId = "";
        $GetsetId = "";
        $memQuesImgUrl = "";

        foreach ($GetWord->result() as $row) {
            $GetWords[] = $row->memQuesType;
            $MemQuesId = $row->memQuesId;
            $GetsetId = $row->setId;
            $GetsetIdarray[] = $row->setId;
            $GetmemQuesImgUrl[] = $row->memQuesImgUrl;

            $worddata[] = array(
                'GetWords' => $row->memQuesType,
                'MemQuesId' => $row->memQuesId,
                'GetsetId' => $row->setId,
                'GetmemuesImgUrl' => $row->memQuesImgUrl);
        }

I expect errorless word shuffle from database and show me the next page

could somebody give me hint what i'm going wrong?

You need to define $worddata as an array before you start referring to its elements by using the brackets. You are also failing to define $GetsetIdarray and $GetmemQuesImgUrl as arrays before trying to append elements to those vars.

$this->db->select('*');
        $this->db->from('tbl_memory_questions');
        $this->db->order_by('rand()');
        $this->db->limit(1);
        $GetWordsFromdb = $this->db->where('memQuesType', 'Words');
        $GetWord = $GetWordsFromdb->get(); print_r($GetWord->result());exit;
        $GetWords = array();
        $MemQuesId = "";
        $GetsetId = "";
        $memQuesImgUrl = "";

        $worddata = array(); // define these as arrays before you start
        $GetsetIdarray = array(); // trying to append elements
        $GetmemQuesImgUrl = array();

        foreach ($GetWord->result() as $row) {
            $GetWords[] = $row->memQuesType;
            $MemQuesId = $row->memQuesId;
            $GetsetId = $row->setId;
            $GetsetIdarray[] = $row->setId;
            $GetmemQuesImgUrl[] = $row->memQuesImgUrl;

            $worddata[] = array(
                'GetWords' => $row->memQuesType,
                'MemQuesId' => $row->memQuesId,
                'GetsetId' => $row->setId,
                'GetmemuesImgUrl' => $row->memQuesImgUrl);
        }