php - $result->num_rows 始终返回 0

Question

在阅读了大量的帖子、教程和其他内容之后 - 我想在这里发帖并希望有人可以帮助我。 我尝试了所有能得到的建议，但仍然不起作用。

这是我的代码:

$prep_stmt = "SELECT id, DATE_FORMAT(added,'%d.%M'), title FROM offers ORDER BY added DESC LIMIT ?, ?;";
$stmt = $mysqli->prepare($prep_stmt);
$stmt->bind_param ('ii',$lowlimit, $page);
$stmt->execute();
$stmt->bind_result($id, $added, $title);
while ($stmt->fetch()) {
... # some random output here
}
$count = $stmt->num_rows;
echo "c -> ". $count;exit;

我总是得到“c -> 0”...但是已经有输出...那么我做错了什么？ :/

Answer 1

在访问 num_rows 属性之前，您需要调用 store_result() 方法。

摘自 PHP manual documentation 的评论:

If you do not use mysqli_stmt_store_result(), and immediately call this function after executing a prepared statement, this function will usually return 0 as it has no way to know how many rows are in the result set as the result set is not saved in memory yet.

mysqli_stmt_store_result() saves the result set in memory thus you can immedietly use this function after you both execute the statement AND save the result set.

您的代码应如下所示:

$stmt->execute();
$stmt->store_result();

$stmt->bind_result($id, $added, $title);

while ($stmt->fetch()) {
    # some random output here...
}

$count = $stmt->num_rows;