php - 无法获取对 bool 值上的成员函数 fetch_row() 的行调用

Question

我正在尝试获取 mysql 查询行，但是获取

Fatal error:Call to a member function fetch_row() on boolean.

我做错了什么？

$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

答案在这里

$query->bind_param('ssss',$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();