致命错误调用未定义方法堆栈跟踪：＃0

Question

问题的根源：$db -> listOccurrences();

我试过了：

public function listAbsences()
    {
        $this->connect();
        $sql = "SELECT description FROM records WHERE _ID_Record_Type = 1;"
        $sqlquery = mysqli_query($this->conn, $sql);
        if (mysqli_num_rows($sqlquery) > 0){
            $result = array();
            while($row = mysqli_fetch_assoc($sqlquery)) {
                $result[] = '$row["description"];
            }
            return $result;
        }
        $this->close_connect();
    }

而且：

public function listAbsences()
    {
        $this->connect();
        $sql = "SELECT description FROM records WHERE _ID_Record_Type = 1;"
        $sqlquery = mysqli_query($this->conn, $sql);
        if (mysqli_num_rows($sqlquery) > 0){
            $result = array();
            while($row = mysqli_fetch_assoc($sqlquery)) {
                $result[] = '<li class="list-group-item">'.$row["description"].'</li>';
            }
            return $result;
        }
        $this->close_connect();
    }

而且：

public function listAbsences()
    {
        $this->connect();
        $sql = "SELECT description FROM records WHERE _ID_Record_Type = 1;"
        $sqlquery = mysqli_query($this->conn, $sql);
        if (mysqli_num_rows($sqlquery) > 0){
            $result = "";
            while($row = mysqli_fetch_assoc($sqlquery)) {
                $result .= "<li class='list-group-item'>".$row["description"]."</li>";
            }
            echo $result;
        }
        $this->close_connect();
    }

但我一直有同样的错误：

  

致命错误：未捕获错误：在C：\ xampp \ htdocs \ lar \ start.php中调用未定义的方法db :: listOccurrences（）：堆栈跟踪：在C：\ xampp \ htdocs中抛出＃0 {main}第39行\ lar \ start.php