页面加载时未定义的索引[重复]

the message is

Notice: Undefined index: flag in C:\xampp\htdocs\myfiles\mobile tracking\index.php on line 63

my code is

<?php 
   $stat=$_REQUEST['flag'];
   if($stat=="FAILED")
       {
      echo "Username/password doesnot exists";
   }
?>

</div>

You should check if the $_REQUEST['flag'] variable has been set:

<?php 
$stat= ( isset($_REQUEST['flag']) ? $_REQUEST['flag'] : null) ;
if($stat=="FAILED")
{
    echo "Username/password doesnot exists";
}

?>

You received a notice because you didn't initialized the values of the array. Use this construction to prevent them.

if (! array_key_exists('flag', $_REQUEST)) {
    $_REQUEST['flag'] = whatever value goes here;
}

The global variable $_REQUEST['flag'] is probably having value NULL. This is the reason you are getting this error. Well, try using isset(). to check whether the variable is having any value or not.