How to use php to develop the payment system of Ethereum

This article is about PHP development of Ethereum system. It mainly introduces the use of PHP for smart contract development and interaction, account creation, transactions, transfers, token development, filters and events, etc.

When I first considered implementing payments via cryptocurrency, I looked at available solutions like Stripe. I think the problem with Stripe is that it only allows Bitcoin payments with US merchant accounts, so that's not an option for me. In the Ethereum world, it looks even worse. There are some newer services but they all want to share the cake.

So what do we need to build an Ethereum payment system from scratch?

• A web server running PHP.

• Have at least one Parity node in the private network with RPC enabled.

• Virtual address generator on a network server, such as vanity-eth.

So how does it work?

• Calculate the price of ETH using the current price from coinbase or kraken API.

• Use a dummy generator to generate address pairs and encrypt or transfer the private key to another server.

• Display the generated address to the customer and check the address every few seconds if payment is received.

Theoretically it seems to be no problem, so let's build it.

Step 1: Set up the server

We will use vanity-eth in nodejs to generate the address.

npm install -g vanity-eth@1.0.4"

After installing vanity-eth on Windows:

Also requires some Etherum nodes. I'm using Parity because it's fast and reliable.

Start it with these parameters, but do not expose the nodes directly to the Internet, keep them behind the firewall without port forwarding.

parity --jsonrpc-interface 0.0.0.0 --jsonrpc-hosts="all" --auto-update=all --jsonrpc-cors null

Parity log of completed synchronization:

For faster deployment, you can use Parity Docker containers. Data can also be saved so that you don't have to resynchronize each time the container is remade.

Step 2: Write the payment class

First create a folder called libs and clone the php-ethereum repo into it. The ethereum-php project is a good wrapper for the json-rpc class.

Then we use the following class and save it as ethpay.php. This is the main logic of payment processing. You can use this to:

• Generate address pairs

• Check balances (pending and completed)

• Convert from WEI to ETH

eth = new Ethereum(RPC_IP, RPC_PORT);
        if(!$this->eth->net_version()) die('RPC ERROR');
    }

    / *
    *得到一个地址的余额，
    *来自parity的余额以十六进制形式出现在wei中
    *使用bc数学函数转换它
    * /
    function getBalanceOfAddress($addr)
    {
        $eth_hex = $this->eth->eth_getBalance($addr, 'latest');
        $eth = $this->wei2eth($this->bchexdec($eth_hex));
        $pending_hex = $this->eth->eth_getBalance($addr, 'pending');
        $pending = $this->wei2eth($this->bchexdec($pending_hex));
        return array('balance'=>$eth,'pending'=>$pending);
    }
    function getCurrentPrice($currency='USD')
    {
        $data = json_decode(file_get_contents('https://api.coinbase.com/v2/prices/ETH-'.$currency.'/spot'),true);
        return $data['data']['amount'];
    }
    /*
    *我们将使用vanityeth生成私钥对
    * npm install -g vanity-eth
    *我们必须重新格式化输出字符串以用作JSON
    * /
    function genPair()
    {
        exec('vanityeth', $outputAndErrors, $return_value);
        $answer = implode(NULL,$outputAndErrors);
        $answer = str_replace('address:','"address":',$answer);
        $answer = str_replace('privKey:','"privKey":',$answer);
        $answer = str_replace('\'','"',$answer);
        return json_decode($answer,true);
    }
    //以下功能用于转换和处理大数字
    function wei2eth($wei)
    {
        return bcp($wei,1000000000000000000,18);
    }
    function bchexdec($hex) {
        if(strlen($hex) == 1) {
            return hexdec($hex);
        } else {
            $remain = substr($hex, 0, -1);
            $last = substr($hex, -1);
            return bcadd(bcmul(16, $this->bchexdec($remain)), hexdec($last));
        }
    }
}

Final Step: Integrate with Your Website

There are multiple ways to do this depending on your service .

At API Heaven, we provide each customer with an ETH address where funds can be deposited. The cronjob checks all customer addresses every minute to detect changes. If they add ETH to the address, the balance is converted into API quota, so our customers don't even need to log into the site to add funds.

Sample integration in API Heaven:

Another approach is to calculate a fixed price and save it in the user session. The customer has to pay on the website and you need to AJAX to query the payment received. If the full amount is received, the backend triggers the sale.

Best of all, you don’t need an external service to integrate the Ethereum payment system on your website. Come and learn and play Ethereum together.

Related recommendations:

How to develop an online payment system with PHP

How to develop a virtual domain name system

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