源代码，
<?phpif($_POST[submit]){if($_POST[uername]=="admin"){if($_POST[password]=="admin"){setcookie("cookie", "ok");echo "<script language=\"javascript\">location.href='login.php';</script>";}else{echo "<font color=red>密码错误</font><br>";}}else{echo "<font color=red>用户名错误</font><br>";}}if($_COOKIE['cookie']!='ok'){?>
<form action="#" method="post" name="login" onsubmit="return checklogin();">用户名：<input type=text name=uername /><br>密 码：<input type=password name=password /><br><input type=submit name=submit value=登录 /></form>
<?php }else{ ?><a href="?out=login">退出</a><?php } ?>
<script language=javascript>function checklogin(){if(login.uername.value==""){alert("用户名不能为空！");login.uername.focus();return false;}if(login.password.value==""){alert("密码不能为空！");login.password.focus();return false;}}</script>
，输入帐号密码后会出现以下错误
Cannot modify header information - headers already sent by (output started a
<?phpif($_POST[submit]){if($_POST[uername]=="admin"){if($_POST[password]=="admin"){setcookie("cookie", "ok");echo "<script language=\"javascript\">location.href='login.php';</script>";}else{echo "<font color=red>密码错误</font><br>";}}else{echo "<font color=red>用户名错误</font><br>";}}if($_COOKIE['cookie']!='ok'){?>
<form action="#" method="post" name="login" onsubmit="return checklogin();">用户名：<input type=text name=uername /><br>密 码：<input type=password name=password /><br><input type=submit name=submit value=登录 /></form>
<?php }else{ ?><a href="?out=login">退出</a><?php } ?>
<script language=javascript>function checklogin(){if(login.uername.value==""){alert("用户名不能为空！");login.uername.focus();return false;}if(login.password.value==""){alert("密码不能为空！");login.password.focus();return false;}}</script>
，输入帐号密码后会出现以下错误
Cannot modify header information - headers already sent by (output started a
