fsockopen实现的HTTP请求

1.get方式，code来自于PHP手册：
    <?php
    $url='/new.php'.'?'.urlencode(id).'='.urlencode(88);
    $fp = fsockopen("www.example.com", 80, $errno, $errstr, 30);
    if (!$fp) {
        echo "$errstr ($errno)<br />\n";
    } else {
        $out = "GET / HTTP/1.1\r\n";
        $out .= "Host: www.example.com\r\n";
        $out .= "Connection: Close\r\n\r\n";

        fwrite($fp, $out);
        while (!feof($fp)) {
        echo fgets($fp, 128);
        }
        fclose($fp);
    }
    ?>
//上面的code可以模拟浏览器www.example.com/new.php?id=88
2.post方式:
    <?php
    $host='www.example.com';
    $url='/login.php';
    $data=urlencode(username).'='.urlencode($username).urlencode(password).'='.urlencode($password);
    $fp=fsockopen("www.baidu.com",80,$errno,$errstr,30);
    if (!$fp) {
            echo "$errstr ($errno)<br />\n";
        } else {
            $out = "POST ".$url." HTTP/1.1\r\n";
            $out .= "Host: www.example.com\r\n";
            $out .= "Content-type: application/x-www-form-urlencoded\r\n";
            $out .= "Content-Length: ".$data."\r\n";
            $out .= "Connection: Close\r\n\r\n";
            $out .=$data;

            fwrite($fp, $out);
            while (!feof($fp)) {
            echo fgets($fp, 128);
            }
            fclose($fp);
    ?>
//上面的code可以模拟用户登录www.example.com/login.php
3.get与post的异同：
    -------------------------------------------------
    HTTP请求报文：request-line
            headers (0或有多个)
            /***headers***/
            //name1: content
            //name2: content
            //.....
            /***headers***/
            <blank line>
            body (只对POST请求有效)
    -------------------------------------------------
    HTTP响应报文：status-line
            headers (0或有多个)
            /***headers***/
            //name1: content
            //name2: content
            //.....
            /***headers***/
            <blank line>
            body (只对POST请求有效)
    -------------------------------------------------
从上面的报文格式可以看出，header之间的区分是换行"\r\n"，header于body的区分是空白行，这就算为什么上面get、post最后都有"Connection: Close\r\n\r\n"原因。
get请求的url要经过urlencode编码，这就像浏览器的请求时看到的%23%23的一样，post请求的内容也要经过urlencode编码。
POST请求必需在header中加入"Content-type: application/x-www-form-urlencoded\r\n"和"Content-Length: ".$data."\r\n"，post提交的数据要在"Connection: Close\r\n\r\n"之后发送,因为该数据相当请求的内容是在header之后的.
4.解析响应报文
也许我们只关心报文的头或者body，在报文格式中我们看到header于body的区分是空白行的。
            $headers = "";
                while ($str = trim(fgets($sock,4096)))
                    $headers .= "$str\n";
    
                $body = "";
                while (!feof($sock))
                    $body .= fgets($sock, 4096);
                fclose($sock);
                $this->responseText=$body;
//通过上面的代码就可以将header于body分开
字符串为空时（即空白行）其bool值为false，这样就把header与body分开了。
BTW-参考资料：《TCP/IP详解》卷三13章HTTP
                               HTTPClient类：http://scripts.incutio.com/httpclient/