详解php与ethereum客户端交互

php与ethereum rpc server通信

一、Json RPC

Json RPC就是基于json的远程过程调用，这么解释比较抽象。简单来说，就是post一个json格式的数据调用rpc server中的方法. 而这个json格式是固定的,总的来说有这么几项:

• method: 方法名
• params: 参数列表
• id: 对过程调用的唯一标识号

二、构建一个Json RPC客户端

/**

• Debug state
• @var boolean
  */
  private $debug;

/**

• The server URL
• @var string
  */
  private $url;
  /**
• The request id
• @var integer
  */
  private $id;
  /**
• If true,notifications are performed instead of requests
• @var boolean
  */
  private $notification = false;

/**

• Takes the connection parameters
• @param string $url
• @param boolean $debug
  */
  public function __construct($url,$debug = false) {
  // server URL
  $this->url = $url;
  // proxy
  empty($proxy) ? $this->proxy = '' : $this->proxy = $proxy;
  // debug state
  empty($debug) ? $this->debug = false : $this->debug = true;
  // message id
  $this->id = 1;
  }

/**

• Sets the notification state of the object. In this state,notifications are performed,instead of requests.
• @param boolean $notification
  */
  public function setRPCNotification($notification) {
  empty($notification) ?
  $this->notification = false
  :
  $this->notification = true;
  }

/**

• Performs a jsonRCP request and gets the results as an array
• @param string $method
• @param array $params
• @return array
  */
  public function __call($method,$params) {

// check
if (!is_scalar($method)) {
  throw new Exception('Method name has no scalar value');
}

// check
if (is_array($params)) {
  // no keys
  $params = $params[0];
} else {
  throw new Exception('Params must be given as array');
}

// sets notification or request task
if ($this->notification) {
  $currentId = NULL;
} else {
  $currentId = $this->id;
}

// prepares the request
$request = array(
        'method' => $method,'params' => $params,'id' => $currentId
        );
$request = json_encode($request);
$this->debug && $this->debug.='***** Request *****'."n".$request."n".'***** End Of request *****'."nn";

// performs the HTTP POST
$opts = array ('http' => array (
          'method' => 'POST','header' => 'Content-type: application/json','content' => $request
          ));
$context = stream_context_create($opts);
if ($fp = fopen($this->url,'r',false,$context)) {
  $response = '';
  while($row = fgets($fp)) {
    $response.= trim($row)."n";
  }
  $this->debug && $this->debug.='***** Server response *****'."n".$response.'***** End of server response *****'."n";
  $response = json_decode($response,true);
} else {
  throw new Exception('Unable to connect to '.$this->url);
}

// debug output
if ($this->debug) {
  echo nl2br($debug);
}

// final checks and return
if (!$this->notification) {
  // check
  if ($response['id'] != $currentId) {
    throw new Exception('Incorrect response id (request id: '.$currentId.',response id: '.$response['id'].')');
  }
  if (!is_null($response['error'])) {
    throw new Exception('Request error: '. var_export($response['error'],true));
  }

  return $response['result'];

} else {
  return true;
}

}
}
?>

比较简单的代码，如果比较懒，拿过去用就行了。也可以上packagist.org自己找一个rpc client.

三、调用RPC的两类方法

有两类方法需要调用. 一类是RPC server自带方法，另一类就是合约方法.

RPC server方法调用json格式

RPC Server自带方法的列表

调用自带方法比较简单，参考上述链接，大部分都有示例.

合约方法调用json格式

调用合约方法必须使用自带方法中的eth_call. 而合约方法名称和合约方法参数列表则使用params进行体现,比如: 我们要调用合约中的balanceOf方法,则json数据应该如何构造呢?

首先看看getBalanace的函数实现:

提炼出函数原型:

在geth控制台下运行命令: