php - 判断 PHP mysqli fetch 是否返回数据

Question

我正在尝试从 PHP 网站获取以下代码，并重写以在返回的 SQL 数据为空时进行回显。

<?php
 $mysqli = new mysqli("localhost", "my_user", "my_password", "world");

/* check connection */
if (mysqli_connect_errno()) {
   printf("Connect failed: %s\n", mysqli_connect_error());
   exit();
}

 $city = "Amersfoort";

 /* create a prepared statement */
 if ($stmt = $mysqli->prepare("SELECT District FROM City WHERE Name=?")) {

/* bind parameters for markers */
$stmt->bind_param("s", $city);

/* execute query */
$stmt->execute();

/* bind result variables */
$stmt->bind_result($district);

/* fetch value */
$stmt->fetch();

printf("%s is in district %s\n", $city, $district);

/* close statement */
$stmt->close();
}

/* close connection */
$mysqli->close();
?>

我在确定执行此操作的正确条件时遇到问题。只是寻找有关如何进一步优化此代码的想法。

Answer 1

$rows = $stmt->rowCount();
echo $rows;