libcurl提供了异步调用方式，有两种风格：

• ONE MULTI HANDLE MANY EASY HANDLES：加入多个easy handle后执行curl_multi_perform方法。该方法在php curl扩展中有对应实现。但最后一步curl_multi_perform是阻塞的。

• MULTI_SOCKET，这个是真正的非阻塞方法，但需要自行实现event loop，且封装较为困难，目前在php中没有对应实现。经过调研，curl_multi_socket_action跟php内核结合困难度很高。

除此之外，基本上没有真正的实现异步http请求的php扩展。目前仅有部分纯php实现的版本，比如tsf中的http client实现。使用纯php实现的问题主要受限于http解析的性能。因此考虑将这一模块用扩展的方式来实现。node.js http-parser就是一个很好的c语言的http解析库。 php_http_parser就是对其做的一个封装，在php中暴露出相应的接口。

为了实现真正的非阻塞请求，仍然需要自己实现event loop。目前推荐结合swoole使用，以获得更好的性能。

使用方式

$buffs = array("HTTP/1.1 301 Moved Permanently\r\n","Location: http://www.google.com/\r\n","Content-Type: text/html; charset=UTF-8\r\n","Date: Sun, 26 Apr 2009 11:11:49 GMT\r\n","Expires: Tue, 26 May 2009 11:11:49 GMT\r\n","Cache-Control: public, max-age=2592000\r\n","Server: gws\r\n","Content-Length: 193\r\n","\r\n","\n","\n","
301 Moved
\n","The document has moved\n","here.\r\n"    ,"here.\r\n"    ,"here.\r\n"    ,"here.\r\n"    ,"here.\r\n","\r\n");$hp = new HttpParser();foreach($buffs as $buff){    $ret = $hp->execute($buff);    if($ret !== false){        echo $ret;        break;    }}

虽然http请求可能分包发送，HttpParser会将所有包合并在一起后，出发body事件，然后调用相应的回调方法。诸如header回调，目前暂未实现。另外，此处需要自行实现timeout逻辑。

示例代码是结合swoole_client与swPromise框架实现的一个异步http client。籍此可以实现真正的非阻塞的PHP程序。

class HttpClientFuture implements FutureIntf {    protected $url = null;    protected $post = null;    protected $proxy = false;    public function __construct($url, $post = array(), $proxy = array()) {        $this->url = $url;        $this->post = $post;        if($proxy){            $this->proxy = $proxy;        }    }    public function run(Promise &$promise) {        $cli = new \swoole_client ( SWOOLE_TCP, SWOOLE_SOCK_ASYNC );        $urlInfo = parse_url ( $this->url );        if(!isset($urlInfo ['port']))$urlInfo ['port'] = 80;        $httpParser = new \HttpParser();        $cli->on ( "connect", function ($cli)use($urlInfo){            $host = $urlInfo['host'];            if($urlInfo['port'])$host .= ':'.$urlInfo['port'];            $req = array();            $req[] = "GET {$this->url} HTTP/1.1\r\n";            $req[] = "User-Agent: PHP swAsync\r\n";            $req[] = "Host:{$host}\r\n";            $req[] = "Connection:close\r\n";            $req[] = "\r\n";            $req = implode('', $req);            $cli->send ( $req );        } );        $cli->on ( "receive", function ($cli, $data = "") use(&$httpParser, &$promise) {            $ret = $httpParser->execute($data);            if($ret !== false){                $cli->close();                $promise->accept(['http_data'=>$ret]);            }        } );        $cli->on ( "error", function ($cli) use(&$promise) {            $promise->reject ();        } );        $cli->on ( "close", function ($cli) {        } );        if($this->proxy){            $cli->connect ( $this->proxy['host'], $this->proxy ['port'], 1 );        }else{            $cli->connect ( $urlInfo ['host'], $urlInfo ['port'], 1 );        }    }}

项目主页：http://www.open-open.com/lib/view/home/1448201436622