php - mysqli_num_rows 不能正常工作

Question

我的网站上有一个管理面板，管理员可以在其中创建新页面。他提供页面名称，然后空格或其他字符被 PHP 代码删除，并声明给一个名为 $new_p_id 的变量。这是 mysql 表示例:

php代码检查页面id是否存在，如果存在则PHP代码返回错误。问题是，即使我在表单中键入“home”或“about”，mysqli_num_rows 也返回 0。我不知道出了什么问题。我试过 mysqli_error($con) 但它没有返回任何错误。这是 PHP 代码:

<?php
if(isset($_POST['pagesubmitted'])){
if($_SESSION['a_role']!="administrator"){die("Please log in");}
$new_p_name=preg_replace("/[^A-Za-z0-9 ]/", '', $_POST['new-page-name']);
$new_p_id=strtolower($new_p_name);
$new_p_id=str_replace(" ", "", $new_p_id);
if(empty($new_p_id)){$errorexists=true;echo "<p class=\"red\">Page name cannot be empty!</p>";}
$new_p_url=$new_p_id;

if ($stmte = mysqli_prepare($con, "SELECT p_id FROM site_pages where p_id=?")) {
    mysqli_stmt_bind_param($stmte,"s", $new_p_id);
    mysqli_stmt_execute($stmte);
if(mysqli_stmt_num_rows($stmte)!=0){
$errorexists=true;echo "<p class=\"red\">Page name already exists!</p>";}
mysqli_stmt_close($stmte);
    }

$new_p_location=$_POST['new-page-location'];
$new_p_content=$_POST['new-page-contents'];
if($errorexists){echo "error!";}
if(!$errorexists){
if ($stmt = $con->prepare("INSERT INTO site_pages(p_id,p_name,p_url,p_location,p_content)VALUES(?,?,?,?,?)")){
            $stmt->bind_param('sssss',$new_p_id,$new_p_name,$new_p_url,$new_p_location,$new_p_content);     
            $stmt->execute();

            $stmt->close(); ?>
            <script>alert("Saved. reload the page to see it in header or sidebar.");</script>
   <?php }
    else {
        printf("Prep statment failed: %s\n", $mysqli->error);
    } 
}
}
    ?>

这是 html 表单代码:

<h1>Create a new page</h1>
<form method="post" action="<?php echo DOMAIN ; ?>/enterprise/?edit=page">
<label for="new-page-name">Page name: </label><input type="text" name="new-page-name" id="new-page-name" value="" maxlength="20">
<br />
<label for="new-page-location">Location: </label>
<select name="new-page-location" id="new-page-location">
<option value="header">Header</option>
<option value="footer">Footer</option>
<option value="header,footer">Header and Footer</option>
<option value="sidebar">Sidebar</option>
<option value="none" selected>None</option>
</select><br />
<label for="new-page-contents">Content:</label><textarea name="new-page-contents" id="new-page-contents"></textarea>
<input type="submit" name="pagesubmitted" class="button" value="Save"/>
</form>

有人可以解释一下哪里出了问题吗？为什么即使页面 id 存在，mysqli_num_rows 也返回 0？

Answer 1

The use of mysqli_stmt_num_rows() depends on whether or not you used mysqli_stmt_store_result() to buffer the entire result set in the statement handle.

http://php.net/manual/ro/mysqli-stmt.num-rows.php

执行后添加

mysqli_stmt_store_result($stmte);