PHP错误:mysqli_num_rows()期望参数1为mysqli_result,给定布尔值

Question

可能重复:
mysql_fetch_array()期望参数1是资源,在select中给出boolean

我在下面收到以下错误.53号线是if(mysqli_num_rows($r) == 1) {.我该如何解决这个问题.

PHP error: on line 53: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given

这是PHP MySQL代码.

$d = "UPDATE users SET del = 1, del_date = NOW() WHERE userid = '" . $_SESSION['userid'] . "'";
$r = mysqli_query ($mysqli, $d) or trigger_error("Query: $d\n<br />MySQL Error: " . mysqli_error($mysqli));

if(mysqli_num_rows($r) == 1) {

Answer 1

mysqli_query为UPDATE查询返回一个布尔值.见http://php.net/manual/en/mysqli.query.php.你可能想要这样的东西:

if (mysqli_affected_rows() == 1) {
    // ...
}