用PHP模拟登陆

<?php
/*
 * 得到网页内容
 * 参数：$host [in] string
 * 主机名称（例如： www.etoow.com）
 * 参数：$method [in] string
 * 提交方法：POST, GET, HEAD ... 并加上相应的参数( 具体语法参见 RFC1945，RFC2068 )
 * 参数：$str [in] string
 * 提交的内容
 * 参数：$sessid [in] string
 * PHP的SESSIONID
 *
 * @返回 网页内容 string
*/
function GetWebContent($host, $method, $str, $sessid = '') {
    $ip = gethostbyname($host);
    $fp = fsockopen($ip, 80);
    if (!$fp) return;
    fputs($fp, "$methodrn");
    fputs($fp, "Host: $hostrn");
    if (!empty($sessid)) {
        fputs($fp, "Cookie: PHPSESSID=$sessid; path=/;rn");
    }
    if (substr(trim($method) , 0, 4) == "POST") {
        fputs($fp, "Content-Length: " . strlen($str) . "rn"); // 别忘了指定长度
        
    }
    fputs($fp, "Content-Type: application/x-www-form-urlencodedrnrn");
    if (substr(trim($method) , 0, 4) == "POST") {
        fputs($fp, $str . "rn");
    }
    while (!feof($fp)) {
        $response.= fgets($fp, 1024);
    }
    $hlen = strpos($response, " "); // LINUX下是 " "
    $header = substr($response, 0, $hlen);
    $entity = substr($response, $hlen4);
    if (preg_match('/PHPSESSID=([0-9a-z] );/i', $header, $matches)) {
        $a['sessid'] = $matches[1];
    }
    if (preg_match('/Location: ([0-9a-z_?=&#.] )/i', $header, $matches)) {
        $a['location'] = $matches[1];
    }
    $a['content'] = $entity;
    fclose($fp);
    return $a;
}
/* 构造用户名，密码字符串 */
$str = ("username=test&password=test");
$response = GetWebContent("localhost", "POST /login.php HTTP/1.0", $str);
echo $response['location'] . $response['content'] . "<br>";
echo $response['sessid'] . "<br>";
if (preg_match('/error.php/i', $response['location'])) {
    echo "登陆失败<br>";
} else {
    echo "登陆成功<br>";
    // 不可以访问user.php，因为不带sessid参数
    $response = GetWebContent("localhost", "GET /user.php HTTP/1.0", '', '');
    echo $response['location'] . "<br>"; // 结果：error.php?errcode=2
    // 可以访问user.php
    $response = GetWebContent("localhost", "GET /user.php HTTP/1.0", '', $response['sessid']);
    echo $response['location'] . "<br>"; // 结果：user.php
    
}
?>