php - 无法从我的数据库类访问连接详细信息

Question

嗨，我正在使用 oophp 创建注册和登录系统，我正在尝试检查数据库中是否已存在电子邮件或用户名，但是当我尝试调用数据库类时，我不断收到这些错误，任何帮助都会受到赞赏。

Notice: Undefined variable: Database in C:\Users\josh\xampp-win32-1.8.3-5-VC11\xampp\htdocs\oop_system\include\class.user.php on line 14

Notice: Trying to get property of non-object in C:\Users\josh\xampp-win32-1.8.3-5-VC11\xampp\htdocs\oop_system\include\class.user.php on line 14

Fatal error: Call to a member function query() on a non-object in C:\Users\josh\xampp-win32-1.8.3-5-VC11\xampp\htdocs\oop_system\include\class.user.php on line 14

用户类别

<?php 
    include "db_config.php";

    class User{

        /*** for registration process ***/
        public function reg_user($name,$username,$password,$email){


            $password = md5($password);
            $sql="SELECT * FROM users WHERE uname='$username' OR uemail='$email'";

            //checking if the username or email is available in db
            $check =  $Database->getConnection->query($sql) ;
            $count_row = $check->num_rows;

            //if the username is not in db then insert to the table
            if ($count_row == 0){
                $sql1="INSERT INTO users SET uname='$username', upass='$password', fullname='$name', uemail='$email'";
                $result = mysqli_query($this->db,$sql1) or die(mysqli_connect_errno()."Data cannot inserted");
                return $result;
            }
            else { return false;}
        }
    }
?>

db_config 类

<?php
/*
* Mysql database class - only one connection alowed
*/
class Database {
    private $_connection;
    private static $_instance; //The single instance
    private $_host = "localhost";
    private $_username = "root";
    private $_password = "";
    private $_database = "oop";
    /*
    Get an instance of the Database
    @return Instance
    */
    public static function getInstance() {
        if(!self::$_instance) { // If no instance then make one
            self::$_instance = new self();
        }
        return self::$_instance;
    }
    // Constructor
    private function __construct() {
        $this->_connection = new mysqli($this->_host, $this->_username, 
        $this->_password, $this->_database);

        // Error handling
        if(mysqli_connect_error()) {
            trigger_error("Failed to conencto to MySQL: " . mysql_connect_error(),
                 E_USER_ERROR);
        }
    }
    // Magic method clone is empty to prevent duplication of connection
    private function __clone() { }
    // Get mysqli connection
    public function getConnection() {
        return $this->_connection;
    }
}
?>

Answer 1

1. Database 是一个类，而不是变量，因此您可以使用 Database 来调用它，而不是 $Database。
2. getConnection 是一个函数/方法，而不是变量/字段，因此您必须在其名称后使用括号:getConnection()。
3. getConnection 是一个非静态函数，因此您无法在 Database 上调用它，您必须获取该类的实例(使用 >数据库::getInstance())。

总而言之，替换这一行:

$check = $Database->getConnection->query($sql);

这样:

$check = Database::getInstance()->getConnection()->query($sql);