php封装mysql类

<?php
class MySQLDB {
    private $host;
    private $username;
    private $password;
    private $dbname;
    private $conn;

    public function __construct($host, $username, $password, $dbname) {
        $this->host = $host;
        $this->username = $username;
        $this->password = $password;
        $this->dbname = $dbname;
        $this->connect();
    }

    private function connect() {
        $this->conn = mysqli_connect($this->host, $this->username, $this->password, $this->dbname);
        if (!$this->conn) {
            die("连接失败: " . mysqli_connect_error());
        }
    }

    public function query($sql) {
        return mysqli_query($this->conn, $sql);
    }

    public function fetch_assoc($result) {
        return mysqli_fetch_assoc($result);
    }

    public function close() {
        mysqli_close($this->conn);
    }
}

// 使用示例
$db = new MySQLDB("localhost", "root", "password", "testdb");
$result = $db->query("SELECT * FROM users");
while ($row = $db->fetch_assoc($result)) {
    echo $row['username'] . "<br>";
}
$db->close();
?>