php连接mysql数据库 封装成类

<?php
class MySQLDB {
    private $host = "localhost";
    private $username = "your_username";
    private $password = "your_password";
    private $dbname = "your_dbname";
    private $conn;

    // 构造函数，连接数据库
    public function __construct() {
        $this->conn = new mysqli($this->host, $this->username, $this->password, $this->dbname);
        if ($this->conn->connect_error) {
            die("连接失败: " . $this->conn->connect_error);
        }
    }

    // 查询操作
    public function query($sql) {
        return $this->conn->query($sql);
    }

    // 插入操作
    public function insert($table, $data) {
        $keys = implode(', ', array_keys($data));
        $values = implode(', ', array_map(function($value) { return "'$value'"; }, array_values($data)));
        $sql = "INSERT INTO $table ($keys) VALUES ($values)";
        return $this->conn->query($sql);
    }

    // 更新操作
    public function update($table, $data, $where) {
        $set = implode(', ', array_map(function($key, $value) { return "$key = '$value'"; }, array_keys($data), array_values($data)));
        $sql = "UPDATE $table SET $set WHERE $where";
        return $this->conn->query($sql);
    }

    // 删除操作
    public function delete($table, $where) {
        $sql = "DELETE FROM $table WHERE $where";
        return $this->conn->query($sql);
    }

    // 析构函数，关闭数据库连接
    public function __destruct() {
        $this->conn->close();
    }
}
?>