致命错误调用未定义方法堆栈跟踪：＃0

Question

Source of the problem: $db -> listOccurrences();

I tried this:

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();
    }

And this:

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();
    }

And this:

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();
    }

But I've kept having the same error:

Fatal error: Uncaught Error: Call to undefined method db::listOccurrences() in C:\xampp\htdocs\lar\start.php:39 Stack trace:#0 {main} thrown in C:\xampp\htdocs\lar\start.php on line 39