PHP 扩展到 MySQLI 类 - PHP extending to the MySQLI class

我创建了一个类，将我的类扩展到 PHP 中的 mysqli 类，看到这些错误我实际上感到震惊

Warning: Missing argument 1 for BeatBeast_Database::__construct(), called in C:'xampp'htdocs'beatbeast'login.php on line 11 and defined in C:'xampp'htdocs'beatbeast'includes'Db'BeatBeast_Db.php on line 6
Warning: Missing argument 2 for BeatBeast_Database::__construct(), called in C:'xampp'htdocs'beatbeast'login.php on line 11 and defined in C:'xampp'htdocs'beatbeast'includes'Db'BeatBeast_Db.php on line 6
Warning: Missing argument 3 for BeatBeast_Database::__construct(), called in C:'xampp'htdocs'beatbeast'login.php on line 11 and defined in C:'xampp'htdocs'beatbeast'includes'Db'BeatBeast_Db.php on line 6
Warning: Missing argument 4 for BeatBeast_Database::__construct(), called in C:'xampp'htdocs'beatbeast'login.php on line 11 and defined in C:'xampp'htdocs'beatbeast'includes'Db'BeatBeast_Db.php on line 6

这是BeatBeast_Db.php

<?php
    class BeatBeast_Database extends mysqli
    {
        protected $r = 'Something';
        public function __construct($db_host,$db_username,$db_password,$db_name)
        {
            parent::__construct($db_host,$db_username,$db_password,$db_name);
            if(mysqli_connect_error())
            {
                die('Connect Error (' . mysqli_connect_errno() . ')' . mysqli_connect_error());
            }
        }
        public function close()
        {
            $this->close();
        }
    }
    require_once("db_constants.inc.php");
    $conn = new BeatBeast_Database("localhost", "root", "myPass", "beatbeast");

这是我的登录名.php

<?php require_once("./includes/Utilities.php") ;?>
<?php require_once("./includes/Db/DatabaseUtilities.php"); ?>
<?php require_once("./includes/Db/Accounts.php");?>
<?php require_once("./includes/Db/BeatBeast_Db.php"); ?>
<?php 
    if(isset($_POST['submit'])){
        require_once("./includes/process_form.inc.php");
        $hashedPass = crypt($password,$username);
        $accounts = new Accounts();
        $accounts->showMessage();

第 11 行是

$accounts = new Accounts();

如果你们有兴趣，这里是我的会计课

require_once（"BeatBeast_Db.php"）;

Class Accounts extends BeatBeast_Database
{
    private $accnt_id;
    private $username;
    private $email;
    function info()
    {
        echo "{$this->accnt_id} {$this->username} {$this->email}";
    }
    public static function getIdByUsername($username)
    {
        global $conn;
        $sql = "SELECT accnt_id FROM accounts WHERE username = '{$username}'";
        $rs = $conn->query($sql);
        $found = $rs->fetch_array();
        return $found;
    }
    public function showMessage(){
        echo "{$this->r}";
    }
    public static function getUsernameById($id)
    {
        global $conn;
            $sql = "SELECT username FROM accounts WHERE accnt_id = $id ";
        $rs = $conn->query($sql);
        $found = $rs->fetch_array();
        return $found;
    }
    public function getAccntId()
    {
        return $this->accnt_id;
    }
    public function getUsername()
    {
        return $this->username;
    }
    public function getEmail()
    {
        return $this->email;
    }
}

如果你看一下MySQLi（http://www.php.net/manual/en/class.mysqli.php）的PHP参考，原始类构造函数包含6个参数：

__construct ([ string $host = ini_get("mysqli.default_host") [, string $username = ini_get("mysqli.default_user") [, string $passwd = ini_get("mysqli.default_pw") [, string $dbname = "" [, int $port = ini_get("mysqli.default_port") [, string $socket = ini_get("mysqli.default_socket") ]]]]]] )

在扩展MySQLi时，即使你没有使用，你也必须定义所有这些。但是，这不是导致警告错误的原因。

在您的情况下，您在不定义任何参数的情况下调用$accounts = new Accounts();。不过，Accounts类范围BeatBeast_Database。因此，您需要传递所有BeatBeast_Database构造函数参数（$db_host,$db_username,$db_password,$db_name）。

让我们从 login.php 第 11 行开始

$accounts = new Accounts();

这将调用 Accounts 类的构造函数 - 该构造函数未定义。因为

Class Accounts extends BeatBeast_Database

PHP 回退到 BeatBeast_Database 类的构造函数：

public function __construct($db_host,$db_username,$db_password,$db_name)

它需要 4 个参数，但没有得到任何参数 - 正是错误消息中的内容。您需要将login.php的第 11 行更改为

$accounts = new Accounts(DB_HOST, DB_USER, DB_PASSWD, DB_NAME);

或者，您在db_constants.inc.php中定义的常量将被保留。