1、判斷是否登錄(check_login.php)

<?php
header("Content-type: text/html; charset=utf-8"); 
session_start();
if($_SESSION[‘username‘]==""){
echo "<script>alert(‘請先登錄！‘);window.location.href=‘index.php‘;</script>";
exit();
}
?>

2、用戶登錄並保持會話

<formname="form"method="post"action="checkuser.php">
<!--
<?php
if(!isset($_SESSION[‘username‘])){//判斷是否登錄
?>
-->
 
用戶名:<inputname=usersize="10"><br/> //沒登錄則顯示輸入用戶名密碼登錄
密碼:<inputname=pwdtype=password>
<inputtype=‘submit‘value=‘登錄‘name=‘submit‘ />
<inputtype=‘reset‘value=‘重置‘name=‘reset‘ />
 
<!--
<?php
}
 
else{ //如果已登錄則顯示提示語
echo ‘歡迎您的光臨！‘;
} ?>  
--> 
 
</form>

<?php
session_start();
include "inc/conn.php";
$username=$_POST[user];
$password=$_POST[pwd];
 
$sql=mysql_query("select * from user where username=‘".$username."‘ and password=‘".$password
 
."‘");
if ($result = mysql_fetch_array($sql)){    $_SESSION[username]=$username; //其他頁面通過判斷是否設置$_SESSION[username]來判斷登錄狀態
?>
 
<scriptlanguage="javascript">
alert("登錄成功");window.location.href="file.php";
</script>
 
<?php
}else{
?>
 
<scriptlanguage="javascript">
alert("對不起，您輸入的用戶名或密碼不正確，請重新輸入!");window.location.href="index.php";
</script>
 
<?php
}
?>

<?php
session_start();//啟動會話
session_unset();//刪除會話
session_destroy();//結束會話
header("location: index.php");
?>

【PHP原生】Session登錄判斷與註銷