PHP 5.4.12：未定义的索引错误

Hey there stackoverflow community!

I'm currently working on a inter-game + inter-server project but I'm getting stuck on my authentication system. When I login with some correct details I get the error

 Notice: Undefined index: myusername in C:\wamp\www
ew\panel.php on line 8
 Notice: Undefined index: mypassword in C:\wamp\www
ew\panel.php on line 9

 Warning: mysqli_fetch_array() expects parameter 1 to be mysqli_result, boolean given in C:\wamp\www
ew\panel.php on line 13

I dont know how to fix this so what i'm asking is How do i fix this?

This is the code I am using to check the login details:

<?php

ob_start();
$host="localhost"; // Host name
$username="mindfulbank"; // Mysql username
$password=""; // Mysql password
$db_name="mindful_bank"; // Database name
$tbl_name="members"; // Table name

// Connect to server and select databse.
mysql_connect("$host", "$username", "$password")or die("Database cannot connect securely, please check back later!");
mysql_select_db("$db_name")or die("Database Cannot Be Selected");

// Define $myusername and $mypassword
$myusername=$_POST['myusername'];
$password=$_POST['mypassword'];
$sha1password=sha1($password);
$mypassword=md5($sha1password);

// 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;
session_start();
header("location:panel.php");
}
else {
echo "Wrong Username or Password";
}

ob_end_flush();
?>

and the page that these errors acctually causes the error:

<?php
session_start();

if(isset($_SESSION['myusername'])){
header("location:logout.php");
}

$myusername=$_SESSION['myusername'];
$mypassword=$_SESSION['mypassword'];
$con=mysqli_connect("localhost","mindfulbank","","mindful_bank");
$result = mysqli_query($con,"SELECT level FROM members WHERE password = '$mypassword' and username = '$myusername'");
$fname = mysqli_query($con,"SELECT name FROM members WHERE password = '$mypassword' and username = '$myusername'");
while($row = mysqli_fetch_array($result))
{  
  if($row['admin'] == 1){
   require 'panel/admindash.php';
 }
 else
 {
   require 'panel/userdash.php';
}
}
?>

Update the connection on the script used to check login details to mysqli as mysql is depreciated.

Once this is done change the mysql_real_escape_string($myusername); functions to mysqli_real_escape_string($your_connection, $myusername);.

mysqli_real_escape_string expects a db connection as required parameter.

http://php.net/manual/en/mysqli.real-escape-string.php

Then add session_start(); to the top of the script used to check login details!

http://php.net/manual/en/function.session-start.php

Hope this helps

You need a session_start() in the first file as well.

First two errors are occurring because you didn't write session_start() before $_SESSION in first script. Always write it at the top of your script. Last error is because you didn't get any result by running that query. Always check $result->num_rows > 0 before further operations.