What should I do if PHP fails to modify database data?

Solution for unsuccessful modification of database data in php: 1. Open the corresponding PHP file; 2. Obtain the user account and password and connect to the database; 3. Use the username variable to modify the data in the data table; 4. View Error message; 5. Check whether $db is connected correctly and modify it; 6. Check whether the table field name involved in sql in the prepare method is incorrect and modify it correctly.

The operating environment of this tutorial: Windows 7 system, PHP version 8.1, Dell G3 computer.

What should I do if php fails to modify the database data?

Problem description:

PHP cannot modify the database data

I have been stuck in ERROR for a whole day, please help me.
The core error report is as shown in the figure:

The complete code is here:

<?php
header(&#39;Content-Type:textml;charset=utf-8&#39;); $username=&#39;游客&#39;;
//获取用户输入的账号和密码并连接数据库
$account=$_POST[&#39;account&#39;]; $password=$_POST[&#39;password&#39;];
$db=new mysqli(&#39;localhost&#39;,&#39;root&#39;,&#39;12345678&#39;,&#39;newsmanage&#39;);
//查询数据库是否已经有相同账号
$query1=$db->prepare("SELECT account FROM user");
$query1->bind_result($theaccount); $query1->execute();
while($query1->fetch()) { if ($account == $theaccount) { echo &#39;<script>alert("该账号已被注册！");
location.href="register.html"</script>&#39;; exit(); } }
//将用户输入的账号和密码写入数据库
$add=$db->prepare("INSERT INTO user VALUES (null,&#39;general&#39;,null,?,?)");
$add->bind_param(&#39;ss&#39;,$account, $password); $add->execute();
//数据库对添加的新用户自动生成唯一ID，查寻此ID并赋值变量
$query2=$db->prepare("SELECT userid FROM user WHERE account=&#39;$account&#39;");
$query2->bind_result($userid); $query2->execute(); $query2->fetch();
//用username变量修改数据表中的数据
$edit=$db->prepare("UPDATE user SET username=? WHERE account=?");
$edit->bind_param(&#39;ss&#39;,$username,$account); $edit->execute();
//报错提示：Call to a member function bind_param() on boolean in echo &#39;<script>alert("恭喜您，注册成功！");
location.href="../login/login.html"</script>&#39;;

Problem analysis:

The error message has made it very clear, saying that you used a member function on a bool value. This error message indicates that your $db->prepare() method failed to execute and returned false instead of the mysqli_stmt object. Please confirm whether $db is connected correctly and whether the table field names involved in the sql in the prepare method are incorrect. and other questions that I can't think of at the moment. . .

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