如何在php中使用mvc连接到数据库[重复]

Question

dbconnect.php

class dbconnect
{
    public function connect()
    {
        $host = 'localhost';
        $user = 'root';
        $pass = '';
        $db = 'demo';
        $connection = mysqli_connect($host, $user, $pass, $db);
        return $connection;
    }
}

dao.php

include 'dbconnect.php';
class dao extends dbconnect
{
    private $conn;
    function __construct()
    {
        $dbcon = new dbconnect();
        $conn = $dbcon->connect();
    }
    function select($table, $where = '', $other = '')
    {
        if (!$where = '') {
            $where = 'where' . $where;
        }
        $sele = mysqli_query($this->conn, "SELECT * FROM  $table $where $other") or die(mysqli_error($this->conn));
        echo $sele;
        return $sele;
    }
}

controller.php

include 'dao.php';
$d = new dao();
if (isset($_POST['btn_login'])) {
    extract($_POST);
    $username = $_POST['user_name'];
    $pswd = $_POST['pswd'];
    $sel = $d->select("users", "email_id = '" . $username . "'AND password='" . $pswd . "'") or die('error from here');
    $result = mysqli_fetch_array($sel);
    if ($result['email_id'] == $username && $result['password'] == $pswd) {
        SESSION_START();
        $_SESSION['user_name'] = $result['email_id'];
        $_SESSION['message'] = 'Invalid Username Or Password';
        header("location:index.php");
    } else {
        $_SESSION['error'] = 'Invalid Username Or Password';
    }
}

我遇到了一个错误

• 警告：mysqli_query() 期望参数 1 为 mysqli，在第 13 行的 /opt/lampp/htdocs/ankit_demo/dao.php 中给出 null

• 警告：mysqli_error() 期望参数 1 为 mysqli，在第 13 行的 /opt/lampp/htdocs/ankit_demo/dao.php 中给出 null

请帮我解决这个问题。

Answer 1

试试这个，if 条件和 where 条件都有问题。而且我们无法回显对象或无法将对象转换为字符串。

dbconnect.php：

<?php
class dbconnect{
    public function connect(){
         $host = 'localhost';
         $user = 'root';
         $pass = '';
         $db = 'demo';
         $connection = mysqli_connect($host,$user,$pass,$db); 
         return $connection;
     }
}

dao.php:

<?php
include 'dbconnect.php';
class dao extends dbconnect {
    private $conn; 
    public function __construct() { 
       $dbcon = new parent(); 
       // this is not needed in your case
       // you can use $this->conn = $this->connect(); without calling parent()
       $this->conn = $dbcon->connect();
    }

    public function select( $table , $where='' , $other='' ){
       if($where != '' ){  // condition was wrong
         $where = 'where ' . $where; // Added space 
       }
       $sql = "SELECT * FROM  ".$table." " .$where. " " .$other;
       $sele = mysqli_query($this->conn, $sql) or die(mysqli_error($this->conn));
       // echo $sele; // don't use echo statement because - Object of class mysqli_result could not be converted to string
       return $sele;
    }
   }
?>

controller.php:

<?php
include 'dao.php';

$d = new dao();

if(isset($_POST['btn_login'])){
    extract($_POST);
    $username = $_POST['user_name'];
    $pswd = $_POST['pswd'];

    $sel = $d->select("users" , "email_id = '" . $username . "' AND password='" . $pswd . "'" ) or die('error from here');
    $result = mysqli_fetch_array($sel) ;

    if($result['email_id'] == $username && $result['password'] == $pswd){
        SESSION_START();
        $_SESSION['user_name'] = $result['email_id'];
        $_SESSION['message'] = 'Invalid Username Or Password';
        header("location:index.php");
    }
    else{
        $_SESSION['error'] = 'Invalid Username Or Password';
        // header("Location:login.php");
    }
}
?>

Answer 2

将构造函数的名称从 __dao() 更改为 __construct()。

将第 6 行代码替换为：

$this->conn = $dbcon->connect();

Answer 3

试试这个：

include 'dbconnect.php';
    class dao extends dbconnect{
        private $conn; 
        function __construct(){ 
            $dbcon = new dbconnect();
            $this->conn = $dbcon->connect();
        }
        function select( $table , $where='' , $other='' ){
            if(!$where = '' ){
                $where = 'where' . $where;
            }
            $sql = "SELECT * FROM  ".$table." " .$where. " " .$other";
            $sele = mysqli_query($this->conn, $sql) or die(mysqli_error($this->conn));
            echo $sele;
            return $sele;
        }
    }

Answer 4

连接文件：

class dbconnect{
    public function connect(){
        $host = 'localhost';
        $user = 'root';
        $pass = '';
        $db = 'demo';
        $connection = mysqli_connect($host,$user,$pass,$db); 
        return $connection;
    }
}

dao 文件：

include 'dbconnect.php';
class dao extends dbconnect {
    private $conn; 
    public function __construct() { 
        $dbcon = new parent(); // this is not needed in your case
        // you can use $this->conn = $this->connect(); without calling parent()
        $this->conn = $dbcon->connect();
    }
    public function select( $table , $where='' , $other='' ){
        if(!$where = '' ){
            $where = 'where' . $where;
        }
        $sele = mysqli_query($this->conn,"SELECT * FROM  $table $where $other") or die(mysqli_error($this->conn));
        echo $sele;
        return $sele;
    }
}

但我认为使用 PDO 会更好，或者像 laravel eloquent 这样的 ORM 系统会更好。