session和cookie区别：
<?php
session_start(); //session_start();必须写在所有的php代码前边
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
</head>
<body>
1.session
(1)session存储在服务器的
(2)session每个人存一份
(3)session有默认的过期时间
(4)session里面可以存储任意类型的数据
安全，对服务造成压力
用法：
1.当一个页面需要使用session的时候，需要在页面顶部加session_start();
2.操作session
赋值 $_SEESION["uid"] = "";
取值 $_SESSINO["uid"]
2.cookie
(1)cookie存储在客户端的
(2)cookie每人存一份
(3)cookie没有默认过期时间
(4)cookie只能存储字符串
不安全，不会对服务器造成压力
用法：
1.操作cookie
赋值：setcookie(key,value)
取值：$_COOKIE["uid"]
<?php
$_SESSION["uid"] = "zhangsan";
setcookie("uid","lisi");
?>
</body>
</html>
<?php
session_starts();
if(empty(session["uid"]))
{
hrader("location:页面.php"); //此方法可设定用户必须走登录界面
exit;
}
登录页面：
<style type="text/css">
.a{ float:left}
.b{ margin-left:70px}
</style>
</head>
<body>
<form action="uidcl.php" method="post">
<table width="45%" border="1">
<tr><td colspan="2"><h1>开发部内部留言板</h1></td></tr>
<tr>
<td>用户名:</td>
<td><input type="text" name="uid" /></td>
</tr>
<tr>
<td>口令:</td>
<td><input type="password" name="pwd" /></td>
</tr>
<tr>
<td colspan="2">
<div class="b">
<input type="submit" value="登录" />
<input type="reset" value="复位" />
</div>
</td>
</tr>
</table>
</form>
</body>
登录处理页面：session_starts();缓存用户名方式,在添加信息处理页面和主页面提取
<?php
session_start();
?>
<?php
$uid = $_POST["uid"];
$pwd = $_POST["pwd"];
include("../fzl/czy.class.php");
$db = new czy();
$sql = "select password from yuangong where username = '{$uid}'";
$attr = $db->strQuery($sql);
//var_dump($attr);
if($pwd == $attr && !empty($pwd))
{
$_SESSION["uid"]=$uid;
header("location:main.php");
}
else
{
echo "用户名或密码错误";
}
?>
主页面：查询：-----
<body>
<?php
session_start();
?>
<table width="40%">
<tr>
<td><a href = "maincl.php"><div class="a"><h3>发布信息</h3></div></a></td>
<td><a href="uid.php"><div class="a"><h3>退出系统</h3></div></a></td>
</tr>
<tr>
<td><h4>留言信息:</h4></td>
</tr>
</table>
<form action="main.php" method="post">
<table width="80%" border="1" cellpadding="0" cellspacing="0">
<tr>
<td>发送人</td>
<td>发送时间</td>
<td>接受人</td>
<td>信息内容</td>
</tr>
<?php
$ss = "";
if(!empty($_POST["ss"]))
{
$ss = $_POST["ss"];
}
$uid = $_SESSION["uid"];
include("../fzl/czy.class.php");
$db = new czy();
$tj = " 1=1 ";
if($_SESSION["uid"] != "" && $_POST["ss"] != "")
{
$tj = " sender = '{$uid}' or recever = '{$uid}' ";
}
$sql = "select * from liuyan where ".$tj;
$attr = $db->Query($sql);
foreach($attr as $v)
{
echo "<tr>
<td>{$v[1]}</td>
<td>{$v[3]}</td>
<td>{$v[2]}</td>
<td>{$v[4]}</td>
</td>";
}
?>
</table>
<div><input id="bb" type="text" name="ss" value="<?php echo "{$uid}" ?>" /><input type="submit" value="查询信息" />
<input type="hidden" name="ss1" /><input type="button" onclick="show(this)" value="清除显示id" /></div>
</form>
</div>
<script type="text/javascript">
function show(a)
{
document.getElementById("bb").value="";
}
</script>
</body>
添加信息页面：
<body>
<table width="300">
<tr>
<td><h3><a href="main.php">查看信息</a></h3></td>
<td><h3><a href="uid.php">退出系统</a></h3></td>
</tr>
<tr>
<td><h4>信息发送:</h4></td>
</tr>
</table>
<form action="chuli.php" method="post">
<table width="300" border="1" >
<tr>
<td>接收人:</td>
<td><input type="text" name="xm" /></td>
</tr>
<tr>
<td>信息内容:</td>
<td><textarea name="nr"></textarea></td>
</tr>
<tr>
<td colspan="2">
<div style="margin-left:85px">
<input type="submit" value="发送" />
<input type="reset" value="复位" />
</div>
</td>
</tr>
</table>
</form>
</body>
添加信息处理页面：
<?php
session_start();
?>
<body>
<?php
$sj = date("Y-m-d H:i:s");
$xm = $_POST["xm"];
$nr = $_POST["nr"];
$uid = $_SESSION["uid"];
include("../fzl/czy.class.php");
$db = new czy();
$sql = " insert into liuyan values ('','$uid','$xm','{$sj}','$nr','') ";
$n = $db->Query($sql,0);
if($n)
{
header("location:main.php");
}
else
{
echo "失败";
}
?>
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