How to use PHP for blockchain development and applications

class Block {
  public $index;
  public $timestamp;
  public $data;
  public $previousHash;
  public $hash;

  public function __construct($index, $timestamp, $data, $previousHash) {
    $this->index = $index;
    $this->timestamp = $timestamp;
    $this->data = $data;
    $this->previousHash = $previousHash;
    $this->hash = $this->calculateHash();
  }

  public function calculateHash() {
    return hash("sha256", $this->index . $this->timestamp . $this->data . $this->previousHash);
  }
}

class Blockchain {
  private $chain;

  public function __construct() {
    $this->chain = [$this->createGenesisBlock()];
  }

  public function createGenesisBlock() {
    return new Block(0, "01/01/2022", "Genesis Block", "0");
  }

  public function getLatestBlock() {
    return $this->chain[count($this->chain) - 1];
  }

  public function addBlock($newBlock) {
    $newBlock->previousHash = $this->getLatestBlock()->hash;
    $newBlock->hash = $newBlock->calculateHash();
    $this->chain[] = $newBlock;
  }

  public function isChainValid() {
    $chainLength = count($this->chain);
    for ($i = 1; $i < $chainLength; $i++) {
      $currentBlock = $this->chain[$i];
      $previousBlock = $this->chain[$i - 1];

      if ($currentBlock->hash !== $currentBlock->calculateHash()) {
        return false;
      }

      if ($currentBlock->previousHash !== $previousBlock->hash) {
        return false;
      }
    }
    return true;
  }
}

$blockchain = new Blockchain();

// 添加第一个区块
$blockchain->addBlock(new Block(1, "02/01/2022", ["Amount" => 10]));

// 添加第二个区块
$blockchain->addBlock(new Block(2, "03/01/2022", ["Amount" => 5]));

// 输出区块链
echo json_encode($blockchain, JSON_PRETTY_PRINT);

// 验证区块链是否有效
if ($blockchain->isChainValid()) {
  echo "区块链有效！";
} else {
  echo "区块链无效！";
}

class Transaction {
  public $fromAddress;
  public $toAddress;
  public $amount;

  public function __construct($fromAddress, $toAddress, $amount) {
    $this->fromAddress = $fromAddress;
    $this->toAddress = $toAddress;
    $this->amount = $amount;
  }
}

class Blockchain {
  // ...

  public function createTransaction($transaction) {
    $this->pendingTransactions[] = $transaction;
  }

  public function minePendingTransactions($minerAddress) {
    $block = new Block(count($this->chain), date("d/m/Y H:i:s"), $this->pendingTransactions, $this->getLatestBlock()->hash);
    $block->mineBlock($this->difficulty);
    $this->chain[] = $block;

    $this->pendingTransactions = [
      new Transaction(null, $minerAddress, $this->reward)
    ];
  }
}