How to use this?

[poejanetwork]

I already composer it (composer require attestto/solana-php-sdk) and make a test PHP file

<?php

ini_set('display_errors', 'on');
require_once('sub_api/libs/solana-php-sdk/vendor/autoload.php');
use Attestto\SolanaPhpSdk\Connection;
use Attestto\SolanaPhpSdk\SolanaRpcClient;
// Using a defined method
$client = new SolanaRpcClient(SolanaRpcClient::DEVNET_ENDPOINT);
$connection = new Connection($client); // MAINNET_ENDPOINT
$accountInfo = $connection->getBalance('B7dwR8DSLzwEYzyPKtX5MHhoe2XzfvBHkP759Q5zzM4h');
$getBalance = $accountInfo/1000000000;
  echo "<pre>";
  print_r("balance = ". $getBalance);
  echo "</pre>";

$fromPublicKey = KeyPair::fromSecretKey(['nKsCgMmf9SPMKUFP6GgaSFik7W1BZyfWSGJqCF4itjdpbwiuxdqSsRvV6dzWZDXe7CdoHh5npS3D7v1Qjm6rAow']);
$toPublicKey = new PublicKey('2aGoKx41dPRU6L7HrX33Az6VdFU7C9u7qnE8yF56bqKA');
$instruction = SystemProgram::transfer(
    $fromPublicKey->getPublicKey(),
    $toPublicKey,
    1
);

$transaction = new Transaction(null, null, $fromPublicKey->getPublicKey());
$transaction->add($instruction);

$txHash = $connection->sendTransaction($transaction, $fromPublicKey);
echo "<pre>";
print_r($txHash);
echo "</pre>";

And got this result

10

Fatal error: Uncaught Error: Class "KeyPair" not found in C:\xampp\htdocs\pro.ject\sol.php:16 Stack trace: #0 {main} thrown in C:\xampp\htdocs\pro.ject\sol.php on line 16

Do I miss anything?