无法在布尔值上获取行调用成员函数fetch_row（）

Question

我正在尝试获取mysql查询行，但是获取

  

致命错误：在布尔值上调用成员函数fetch_row（）。

我在这里做错了什么？

$select="visitor_country";
$startDate="2016-01-01";
$endDate="2016-12-31";
$groupBy="visitor_country";

$query=$connection->prepare("SELECT ?, COUNT(*) as count FROM `analytics`.`analytics` WHERE date BETWEEN ? AND ? GROUP BY ? ORDER BY count");
$query->bind_param('ssss',$select,$startDate,$endDate,$select);
$query->execute();
$result=$query->store_result();
$row = $result->fetch_row();

$num_of_rows=count($row);
echo $num_of_rows."<br>";
$query->close();
$connection->close();

Answer 1

这是答案

$query->bind_param('ssss',$select,$startDate,$endDate,$select);
$query->execute();
$result = $query->get_result();
$row = $result->fetch_row();
$num_of_rows=count($row);
echo $num_of_rows."<br>";
$query->close();
$connection->close();