Build a Simple PHP Blockchain from Scratch – Step‑by‑Step Guide

Introduction

Blockchain is a distributed ledger system that links blocks of transaction records using cryptographic hashes. To make the concept concrete for beginners, we implement a simple blockchain in PHP.

Block Definition

<?php
class Block {
    public $prevHash;
    public $hash;
    public $timeStamp;
    public $data;
}

Block Fields

prevHash : hash of the previous block

hash : hash of the current block

timeStamp : creation timestamp

data : stored transaction data

Hash Calculation

<?php
class Block {
    ...
    public function setBlockHash() {
        $data = serialize($this);
        $this->hash = hash('sha256', $data);
    }
}

Block Constructor

<?php
class Block {
    ...
    public function __construct($prevHash, $data) {
        $this->prevHash = $prevHash;
        $this->timeStamp = time();
        $this->data = $data;
        $this->setBlockHash();
    }
    public function getBlockHash() {
        return $this->hash;
    }
}

Blockchain Class

<?php
include('block.php');
class Blockchain {
    public $blocks = [];
    public function __construct() {
        $this->blocks[] = new Block('', 'Genesis Block');
    }
    public function addBlock($data) {
        $prevBlock = $this->blocks[count($this->blocks)-1];
        $this->blocks[] = new Block($prevBlock->getBlockHash(), $data);
    }
}

Testing the Implementation

<?php
include('blockchain.php');
$bc = new Blockchain();
$bc->addBlock('This is block1');
$bc->addBlock('This is block2');
foreach ($bc->blocks as $block) {
    printf("PrevHash: %s
", $block->prevHash);
    printf("Hash: %s
", $block->hash);
    printf("Data: %s
", $block->data);
    printf("
");
}

The output shows each block’s previous hash, current hash, and stored data, confirming that the chain links correctly.

Conclusion

This example demonstrates a minimal PHP blockchain. It lacks features such as distributed consensus, persistent storage, and security hardening, which will be addressed in future tutorials.