$ result-> num_rows始终返回0 [英] $result->num_rows always returns 0

问题描述

在阅读了大量的主题，教程和其他内容之后-我想在这里发布，希望有人可以帮助我. 我尝试了所有可能得到的建议，但仍然没有用.

after reading tons of threads, tutorials and whatever - I feel like posting here and hope that someone can help me. I tried out every advice I could get, but it's still not working.

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" ...但是已经有输出了...所以我在做什么错呢? :/

I always get "c -> 0" ... but there IS output already ... so what am I doing wrong ? :/

推荐答案

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

You need to call the store_result() method before accessing the num_rows property.

来自对 PHP手册文档:

如果不使用mysqli_stmt_store_result()，并在执行准备好的语句后立即调用此函数，则该函数通常将返回0，因为它无法知道结果集中有多少行，因为没有结果集保存在内存中了.

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()将结果集保存在内存中，因此您可以在执行语句并保存结果集后立即使用此功能.

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;

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