Php 使用mysqli和oops创建数据库，并在数据库中插入值

我在插入时出错，所以我感到困惑。请帮助我或向我推荐oop的最佳教程

testdb.php页面

testclass.php页面

post.php

---

将其放在构造函数的参数中：

include 'testdb.php';

public function __construct($fname, $lname, $fullname) 
{
    $this->fname = $fname;
    $this->lname = $lname;
    $this->fullname = $fullname;
    $db = new DB_Class();
    $conn = $db->connect();
    // $db = new mysqli('localhost', 'username', 'password', 'database');
    $result = mysqli_query($conn, "INSERT INTO users(fname, lname, fullname) values ('$this->fname', '$this->lname','$this->fullname')") or die(mysqli_error());
    return $result;
}

然后，初始化：

$userTest = new user($_POST['fname'], $_POST['lname'], $_POST['fullname']);

旁注：既然您使用的是mysqli，为什么不使用准备好的语句呢

编辑：您忘记了

DB\u类上的
返回值
：

class DB_Class 
{
    public $conn;

    public function __construct() 
    {
        $connection = mysqli_connect("localhost", "root", "","test");

        if (mysqli_connect_errno()) {
            echo "Failed to connect to MySQL: " . mysqli_connect_error();
        }
        $this->conn = $connection; // return the mysqli instance
    }

    public function connect()
    {
        return $this->conn;
    }
}

获取错误。创建新用户时，对象的值将被分配并保存到db。之后，您将分配POST变量。您必须从构造函数中获取所有这些信息，或者将变量分配给构造函数。警告：mysqli_query（）要求参数1为mysqli，在$result=mysqli_query行上，我使用了此方法，但在$result=mysqli_query（$db）上出现错误，请插入用户(f@user3364529您确定在此文件中找到了
DB\u类吗？警告：mysqli\u query（）希望参数1是mysqli，我有print print\r（$DB），然后我有DB\u类对象（）@user3364529是
testdb.php
包含在
testclass.php
？
包含“testdb.php”
致命错误：当当前类作用域在这些行上显示未定义变量时没有父项$this->fname=$fname；
include 'testdb.php';

public function __construct($fname, $lname, $fullname) 
{
    $this->fname = $fname;
    $this->lname = $lname;
    $this->fullname = $fullname;
    $db = new DB_Class();
    $conn = $db->connect();
    // $db = new mysqli('localhost', 'username', 'password', 'database');
    $result = mysqli_query($conn, "INSERT INTO users(fname, lname, fullname) values ('$this->fname', '$this->lname','$this->fullname')") or die(mysqli_error());
    return $result;
}

$userTest = new user($_POST['fname'], $_POST['lname'], $_POST['fullname']);

class DB_Class 
{
    public $conn;

    public function __construct() 
    {
        $connection = mysqli_connect("localhost", "root", "","test");

        if (mysqli_connect_errno()) {
            echo "Failed to connect to MySQL: " . mysqli_connect_error();
        }
        $this->conn = $connection; // return the mysqli instance
    }

    public function connect()
    {
        return $this->conn;
    }
}

you can try the below code in 

class user extends DB_Class{

    public $fname;
    public $lname;
    public $fullname;   
    public function __construct() 
    {
        parent::__construct(); //add this line of code 

    }
    public function insert($fname, $lname, $fullname)
    {
        $this->fname = $fname;
        $this->lname = $lname;
        $this->fullname = $fullname;
        $db = new DB_Class();
        $result = mysqli_query($db, "INSERT INTO users(fname, lname, fullname) values ('$this->fname', '$this->lname','$this->fullname')") or die(mysqli_error());
        return $result;
    }
}