为什么mysqli num_rows 总是返回0?

2021-12-25 00:00:00 php mysqli

我一直无法使用 mysqli 获取要返回的行数.尽管肯定有一些结果，但我每次都只返回 0.

I've been having trouble getting the number of rows to return using mysqli. I just get 0 back every time even though there are definitely some results.

if($stmt = $mysqli->prepare("SELECT id, title, visible, parent_id FROM content WHERE parent_id = ? ORDER BY page_order ASC;")){  
    $stmt->bind_param('s', $data->id);  
    $stmt->execute();
    $num_of_rows = $stmt->num_rows;  
    $stmt->bind_result($child_id, $child_title, $child_visible, $child_parent);  

    while($stmt->fetch()){
        //code
    }

    echo($num_of_rows);

    $stmt->close();
}

为什么不显示正确的数字?

Why doesn't it show the correct number?

推荐答案

需要调用mysqli_stmt::store_result() 在 num_rows 查找之前:

You need to call mysqli_stmt::store_result() prior to the num_rows lookup:

if($stmt = $mysqli->prepare("SELECT id, title, visible, parent_id FROM content WHERE parent_id = ? ORDER BY page_order ASC;")){  
    $stmt->bind_param('s', $data->id);  
    $stmt->execute();
    $stmt->store_result(); <-- This needs to be called here!
    $num_of_rows = $stmt->num_rows;  
    $stmt->bind_result($child_id, $child_title, $child_visible, $child_parent);  

    while($stmt->fetch()){
        //code
    }

    echo($num_of_rows);

    $stmt->close();
}

请参阅 mysqli_stmt::num_rows 上的文档，它就在页面顶部附近(在主描述块中).

See the docs on mysqli_stmt::num_rows, it says it right near the top of the page (in the main description block).

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