php封装数据库操作类

<?php
class Database {
    private static $instance;
    private $connection;

    private function __construct($host, $user, $password, $database) {
        $this->connection = new mysqli($host, $user, $password, $database);
        if ($this->connection->connect_error) {
            die("Connection failed: " . $this->connection->connect_error);
        }
    }

    public static function getInstance($host, $user, $password, $database) {
        if (!self::$instance) {
            self::$instance = new Database($host, $user, $password, $database);
        }
        return self::$instance;
    }

    public function query($sql) {
        return $this->connection->query($sql);
    }

    public function escape($string) {
        return $this->connection->real_escape_string($string);
    }

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

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