我的php登录出现致命错误

我的php登录出现致命错误,php,login,fatal-error,Php,Login,Fatal Error,错误是: 致命错误:对未定义函数会话的调用在第3行的C:\xampp\htdocs\sigh\login\u success.php中注册 以下是编码: main_login.php checklogin.php Logout.php 登录\ u suces.php 这里似乎有什么问题?删除会话是从第3行的C:\xampp\htdocs\sigh\login\u success.php注册的 此功能已在PHP5.4中删除 如果出于某种原因需要它,考虑将PHP改为PHP SeStudioIsIsA

错误是:

致命错误:对未定义函数会话的调用在第3行的C:\xampp\htdocs\sigh\login\u success.php中注册

以下是编码:

main_login.php

checklogin.php

Logout.php

登录\ u suces.php

这里似乎有什么问题?

删除会话是从第3行的C:\xampp\htdocs\sigh\login\u success.php注册的

此功能已在PHP5.4中删除


如果出于某种原因需要它,考虑将PHP改为PHP

SeStudioIsIsA},表示为PHP5.3.0,如PHP5.4.0

> P> 从PHP5.3.0开始,此函数已被弃用,并从PHP5.4.0开始删除

检查$\u会话是否处于活动状态

if(isset($_SESSION['login']) && !empty($_SESSION['login']) ){
  //do something
}

避免在数据库中存储纯文本密码…错误消息确实足以理解问题!未定义函数表示该函数不存在。
<?php
session_start();
$host="localhost"; // Host name 
$username="root"; // Mysql username 
$password="1234"; // Mysql password 
$db_name="test"; // Database name 
$tbl_name="members"; // Table name 

// Connect to server and select databse.
mysql_connect("$host", "$username", "$password")or die("cannot connect"); 
mysql_select_db("$db_name")or die("cannot select DB");

// username and password sent from form 
$myusername=$_POST['myusername']; 
$mypassword=$_POST['mypassword']; 

// To protect MySQL injection (more detail about MySQL injection)
$myusername = stripslashes($myusername);
$mypassword = stripslashes($mypassword);
$myusername = mysql_real_escape_string($myusername);
$mypassword = mysql_real_escape_string($mypassword);
$sql="SELECT * FROM $tbl_name WHERE username='$myusername' and password='$mypassword'";
$result=mysql_query($sql);

// Mysql_num_row is counting table row
$count=mysql_num_rows($result);

// If result matched $myusername and $mypassword, table row must be 1 row
if($count==1){

// Register $myusername, $mypassword and redirect to file "login_success.php"

$_SESSION["myusername"]=$myusername;
$_SESSION["mypassword"]=$mypassword;
header("location:login_success.php");
}
else {
echo "Wrong Username or Password";
}
?>
<?php 
session_start();
session_destroy();
?>
<?php
session_start();
if(!session_is_registered(myusername)){
header("location:main_login.php");
}
?>

<html>
<body>
Login Successful
</body>
</html>
if(isset($_SESSION['login']) && !empty($_SESSION['login']) ){
  //do something
}