How to implement a blockchain application in PHP7.0?

With the promotion and popularity of blockchain technology around the world, more and more developers are beginning to pay attention to how to use blockchain technology in their own applications. This article will introduce how to implement a simple blockchain application in PHP7.0.

1. What is blockchain

Blockchain is a decentralized distributed database composed of multiple blocks, each block contains multiple transaction records. . Whenever a new transaction occurs, it will first be verified by the node, then packaged into a new block and added to the blockchain. Since each block contains the hash value of the previous block, the entire blockchain forms an immutable data structure in which no one can change or delete the data.

Blockchain has the characteristics of decentralization, non-tampering, and traceability, so it is widely used in fields such as digital currency, smart contracts, and supply chain management.

2. Blockchain implementation ideas in PHP

To implement a blockchain application in PHP, you first need to implement the following functions:

1. Definition Block class, including block headers, transaction records and other information;
2. implements the hash function, used to calculate the hash value of the block;
3. implements the workload proof algorithm, used to limit new areas The speed of block generation;
4. Defines the blockchain class, including functions such as adding new blocks and verifying the legitimacy of the blockchain.

On this basis, we can implement a simple blockchain application to store digital currency transaction records.

3. Specific steps to implement blockchain in PHP

1. Define block class

Define a Block class, including block headers and transaction records, etc. information.

class Block
{
    public $index;          // 区块序号
    public $timestamp;      // 区块时间戳
    public $transactions;   // 交易记录
    public $prev_block_hash; // 前一个区块的哈希值
    public $nonce;          // 随机数，用于工作量证明算法

    public function __construct(int $index, string $timestamp, array $transactions, string $prev_block_hash)
    {
        $this->index = $index;
        $this->timestamp = $timestamp;
        $this->transactions = $transactions;
        $this->prev_block_hash = $prev_block_hash;
        $this->nonce = 0;
    }

    public function hash(): string
    {
        return hash('sha256', json_encode($this->toArray()));
    }

    public function toArray(): array
    {
        return [
            'index' => $this->index,
            'timestamp' => $this->timestamp,
            'transactions' => $this->transactions,
            'prev_block_hash' => $this->prev_block_hash,
            'nonce' => $this->nonce,
        ];
    }
}

2. Implement the hash function

Implement a sha256 hash function for calculating the hash value of the block.

public function hash(): string
{
    return hash('sha256', json_encode($this->toArray()));
}

3. Implementing the workload proof algorithm

Implementing a simple workload proof algorithm requires that the hash value of the new block must start with a certain number of 0s.

public function proofOfWork(int $difficulty): string
{
    $prefix = str_repeat('0', $difficulty);

    while (substr($hash = $this->hash(), 0, $difficulty) !== $prefix) {
        ++$this->nonce;
    }

    return $hash;
}

4. Define Blockchain Class

Define a Blockchain class, including functions such as adding new blocks and verifying the legitimacy of the blockchain.

class Blockchain
{
    private array $chain;
    private int $difficulty;

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

    public function getLastBlock(): Block
    {
        return end($this->chain);
    }

    public function addBlock(Block $block): void
    {
        $block->prev_block_hash = $this->getLastBlock()->hash();
        $block->proofOfWork($this->difficulty);
        $this->chain[] = $block;
    }

    public function validate(): bool
    {
        foreach (array_slice($this->chain, 1) as $i => $block) {
            if ($block->prev_block_hash !== $this->chain[$i]->hash()) {
                return false;
            }
        }

        return true;
    }

    private function createGenesisBlock(): Block
    {
        return new Block(0, '2020-01-01 00:00:00', [], '');
    }
}

The above is a simple PHP version of blockchain implementation.

4. Summary

Blockchain technology has the characteristics of non-tampering and decentralization, and is widely used in digital currency, smart contracts, supply chain management and other fields. Through a simple PHP implementation, we can have a deeper understanding of the principles and implementation methods of blockchain, laying a foundation for subsequent learning and development.

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