如何在这个文件中实现保存账号密码并写入到一个文件中？
<?require_once("php/report/include/cookie.php");$domain = trim($_SERVER["SERVER_NAME"]);if(file_exists("/var/eyou/apache/htdocs/".$domain)){ include("$domain"); exit;}?><html><title>青岛职业技术学院电子邮件系统</title><meta http-equiv="Content-Type" content="text/html; charset=gb2312"><script language="javascript" src="/js/jquery-1.2.6.js"></script><style type="text/css"><!--.font{ font-family: Arial, Helvetica, sans-serif; font-size: 12px; color: #4c4c4c;}.input { font-family: Arial, Helvetica, sans-serif; font-size: 12px; color: #4c4c4c;}body{ margin: 0px;}.message{ color:red; font-family: Arial, Helvetica, sans-serif; font-size: 12px;}--></style><script language="javascript">$(document).ready(function() { $("#submit").click(function(){ login(); return false; })});function login() { var messageDefault = "系统错误，请稍候再试。"; formData = $("input, select").serialize(); $.ajax({ type: "post", url: "/cgi-bin/user_login", data: formData + "&rnd=" + parseInt(Math.random()*9999), dataType: "html", success: function (dataRes) { switch ($.trim(dataRes)) { case "0": window.location = "/cgi-bin/user_login"; break; case "2": $TxtFileName = "Demo.txt"; //showMessage($TxtFileName); showMessage("您输入的用户或密码错误"); break; case "3": showMessage("本系统已禁止使用别名登录，请使用真实用户名登录。"); break; case "4": showMessage("由于该用户尝试的登录次数达到最大值，已被禁止登录。"); break; case "5": showMessage("您输入的密码错误"); break; case "6": showMessage("该用户已经被锁定"); break; case "7": showMessage("该用户所在的域已经过期"); break; case "8": showMessage("该用户已经过期"); break; case "9": showMessage("您输入的域名错误"); break; case "10": showMessage("用户提交的验证码错误"); break; case "11": showMessage("license过期，请与管理员联系"); break; case "12": showMessage("用户输入的密码过短"); break; case "13": showMessage("导用户信件出错"); break; case "14": showMessage("异常错误"); break; case "15": showMessage("非法用户名"); break; case "16": showMessage("非法域名"); break; case "17": showMessage("您所在的组不允许您用页面登陆邮箱"); break; default: case "1": showMessage(messageDefault); break; } }, error: function () { showMessage(messageDefault); } });}function showMessage(message) { $("#message").html(message);}</script></head><body><form name=login method=post id="login"><table width="995" height="549" align="center" cellpadding="0" cellspacing="0" > <tr> <td width="285" rowspan="3"><img src="/images/pic_zuo.gif" width="289" height="549"></td> <td height="121"><img src="/images/pic_shang.gif" width="418" height="121"></td> <td width="288" rowspan="3"><img src="/images/pic_you.gif" width="288" height="549"></td> </tr> <tr> <td height="308" background="/images/pic_zhong.GIF"><table width="60%" align="center" cellpadding="0" cellspacing="7" > <tr><br><br> <td width="25%" align="right" class="font">用户名：</td> <td width="75%"><input name="LoginName" type="text" class="input" size="18"><br/><span id="message" class="message"></span></td> </tr> <tr> <td align="right" class="font">@</td> <td> <select class=input name=domain style="width:120px"><?$lines = @file(get_config('domain_txt'));if(null == $lines || count($lines)>20){ if(null != $_COOKIE['domainname'] && $_COOKIE['domainname'] != get_config('me')) { ?> <option value="<?= get_config('me') ?>"><?= get_config('me') ?></option> <option value="<?= $_COOKIE['domainname'] ?>" selected><?= $_COOKIE['domainname'] ?></option> <? } else { ?> <option value="<?= get_config('me') ?>"><?= get_config('me') ?></option> <? }}else{ for($i=0; $i<count($lines); $i++) { $lines[$i] = ereg_replace("\r","",$lines[$i]); $lines[$i] = ereg_replace("\n","",$lines[$i]); ?> <option value="<?= $lines[$i] ?>" <?= $_COOKIE['domainname']==$lines[$i]?"selected":"" ?>><?= $lines[$i] ?></option> <? }}?> </select></td> </tr> <tr> <td align="right" class="font">密 码：</td> <td><input name="Password" type="password" class="input" size="18"></td> </tr> <tr> <td align="right" class="font">风 格：</td> <td><select class=input name="skin" style="width:120px "> <option value="">默认</option> <option value="blue">蔚蓝天空</option> <option value="red">橘子红了</option> <option value="silver">银装素裹</option> <option value="purple">紫色情怀</option> <option value="green">绿意盎然</option> </select></td> </tr> <tr> <!-- <td align="right" class="font">语 言：</td> <td colspan="2" class="font"><input name="locale" type="radio" value="zh_CN" checked> 中文 <input type="radio" name="locale" value="en_US"> 英文 <a href="/getpass">找回密码</a></td> <td align="center" class="font" colspan="2" height="25"><a href="/getpass">找回密码</a></td> --> <td align="center" class="font" colspan="2" height="25"><a href="/php/report/osignup.php">邮箱注册</a> <a href="/help/help.html">帮助</a> <a href="http://www.qtc.edu.cn">返回主页</a></td> </tr> <tr> <td height="25"> </td> <td><INPUT id="submit" type=image cache src="/images/menu2.gif" border=0 name=log_in target="_blank"></td> </tr> </table></td> </tr> <tr> <td height="120"><img src="/images/pic_xia.gif" width="418" height="120"></td> </tr></table></FORM></body></html><?php?>