下面直接给出 使用 curl 和 fsockopen 的例子，你可以当成使用实例，也可以直接当作封装好的函数直接使用。

curl函数使用代码

http get 请求：

function httpGet($url) {
    $curl = curl_init();
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($curl, CURLOPT_TIMEOUT, 500);
    curl_setopt($curl, CURLOPT_URL, $url);

    $res = curl_exec($curl);
    curl_close($curl);

    return $res;
}

http post 请求，等待返回结果：（当然你可以通过设置timeout来达到异步的效果： curl_setopt($ch, CURLOPT_TIMEOUT,$second);）

public function xcurl($url,$ref=null,$post=array(),$ua="Mozilla/5.0 (X11; Linux x86_64; rv:2.2a1pre) Gecko/20110324 Firefox/4.2a1pre",$print=false) {
     $ch = curl_init();
     curl_setopt($ch, CURLOPT_AUTOREFERER, true);
     if(!empty($ref)) {
          curl_setopt($ch, CURLOPT_REFERER, $ref);
     }
     curl_setopt($ch, CURLOPT_URL, $url);
     curl_setopt($ch, CURLOPT_HEADER, 0);
     curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
     curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
     if(!empty($ua)) {
          curl_setopt($ch, CURLOPT_USERAGENT, $ua);
     }
     if(count($post) > 0){
          curl_setopt($ch, CURLOPT_POST, 1);
          curl_setopt($ch, CURLOPT_POSTFIELDS, $post);
     }
     $output = curl_exec($ch);
     curl_close($ch);
     if($print) {
          print($output);
     } else {
          return $output;
     }
}

fsockopen 函数使用代码：（异步post 请求）

public function curl_request_async($url, $params, $type='GET')
    {
    // set referer
        $referer = $_SERVER['HTTP_HOST'];
        foreach ($params as $key => &$val) {
            if (is_array($val)) $val = implode(',', $val);
            $post_params[] = $key.'='.urlencode($val);
        }
        $post_string = implode('&', $post_params);

        $parts=parse_url($url);

        @$fp = fsockopen($parts['host'], isset($parts['port'])?$parts['port']:80, $errno, $errstr, 2);

        if(!$fp){
            echo "$errstr ($errno)<br />\n";
        }else{
            if('GET' == $type) $parts['path'] .= '?'.$post_string;

            $out = "$type ".$parts['path']." HTTP/1.1\r\n";
            $out.= "Host: ".$parts['host']."\r\n";
            $out.= "Referer: ".$referer."\r\n";
            $out.= "Content-Type: application/x-www-form-urlencoded\r\n";
            $out.= "Connection: Close\r\n\r\n";
            // Data goes in the request body for a POST request
            if ('POST' == $type && isset($post_string)) $out.= $post_string;
            fwrite($fp, $out);
            /* // 打开这段请求需要等待结果返回
             $receive = '';
              while (!feof($fp)) {
                  $receive .= fgets($fp, 128);
              }
              echo "<br />".$receive;
            */
            usleep(3000); // 不加这段有的时候服务器接收不到请求。大坑.
            fclose($fp);
        }
    }

补充：
php post json数据：

function jcurl($url,$ref=null,$post=array(),$ua="Mozilla/5.0 (X11; Linux x86_64; rv:2.2a1pre) Gecko/20110324 Firefox/4.2a1pre",$print=false) {
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_AUTOREFERER, true);
    if(!empty($ref)) {
        curl_setopt($ch, CURLOPT_REFERER, $ref);
    }
    curl_setopt($ch, CURLOPT_URL, $url);
    if(!empty($ua)) {
        curl_setopt($ch, CURLOPT_USERAGENT, $ua);
    }
    if(is_array($post)){
        $data_string = json_encode($post);
    }else{
        $data_string = $post;
    }
    curl_setopt($ch, CURLOPT_POST, 1);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $data_string);
    curl_setopt($ch, CURLOPT_HTTPHEADER, array(
            'Content-Type: application/json; charset=utf-8',
            'Content-Length: ' . strlen($data_string))
    );
    $output = curl_exec($ch);
    curl_close($ch);
    if($print) {
        print($output);
    } else {
        return $output;
    }
}

这种方式 不能使用 $_POST 接收变量，需要通过

file_get_contents("php://input") 

或

$GLOBALS['HTTP_RAW_POST_DATA'];

获取 post 变量