This is an implementation of a hash tree or Merkle Tree for PHP.
Install via Composer (make sure you have composer in your path or in your project).
Put the following in your package.json:
{
"require": {
"pleonasm/merkle-tree": "*"
}
}Then run composer install.
Usage of a hash tree requires a user to provide a hashing function that each node will use to do its hashing. This function must accept a single string argument and must always return a string. It should never throw an exception.
If desired, you can also provide a callback for when the entire hash tree has been actually finished, rather than checking for it each time yourself.
<?php
use Pleo\Merkle\FixedSizeTree;
require 'vendor/autoload.php';
// basically the same thing bitcoin merkle tree hashing does
$hasher = function ($data) {
return hash('sha256', hash('sha256', $data, true), true);
};
$finished = function ($hash) {
echo implode('', unpack('H*', $hash)) . "\n";
};
$tree = new FixedSizeTree(16, $hasher, $finished);
$tree->set(0, 'Science');
$tree->set(1, 'is');
$tree->set(2, 'made');
$tree->set(3, 'up');
$tree->set(4, 'of');
$tree->set(5, 'so');
$tree->set(6, 'many');
$tree->set(7, 'things');
$tree->set(8, 'that');
$tree->set(9, 'appear');
$tree->set(10, 'obvious');
$tree->set(11, 'after');
$tree->set(12, 'they');
$tree->set(13, 'are');
$tree->set(14, 'explained');
$tree->set(15, '.'); // this will echo the string 'c689102cdf2a5b30c2e21fdad85e4bb401085227aff672a7240ceb3410ff1fb6'The FixedSizeTree implements a Merkle Tree the same way bitcoins do. There are other ways to actually deal with a tree width that is not a perfect square.
If there is a need for the other method, I would not be opposed to adding it.
You can find the license for this code in the LICENSE file