my code gives undefine index error .. and i don't know how to solve it...
i m making online testing program but every eror in every step is undefine index error...
ok my html file is

<html>
<form action = "http://localhost/onlineexam/home.php" method = 'get'>


<center><h1>WELCOME TO ONLINE EXAMINATION</h1>
<br>


<br> User Name    <input type = 'text' name='username'>
<br> Enrolled no <input type = 'text' 

name='enrollno'>


<br>  <input type ='submit' value='Login' >


</form></center>
</body>
</html>

and my php code is 

<?php

$u1=$_GET['username'];
$e1=$_GET['enrollno'];


$ip='localhost';
$user='root';
$pass='';
$con = mysql_connect($ip,$user,$pass);
if(!($con))
die("connection fail");
$db=mysql_select_db('onlinetesting');
if(!($db))
die("<br>database not found");
$querry="select *from login where u_name='$u1',enrolled_no='e1'";
$result= mysql_query($querry);
if($result)
echo("<html>


<center>
<h1> WELCOME $u1</h1>
<h2> CLICK FOR THE TEST START</h2>
 <form action='http://localhost/onlineexam/test.php' method='get'>

   <input type='hidden' name='id' value='1'>

   <input type='submit'  value='Start'>



</form>
</center>

</html>
");
else
echo("SORRY $u1 REGISTERED FIRST<br><a href='registration.html'>CLICK HERE</a>");
?>

but it gives the error

Notice: Undefined index: username in M:xampphtdocsonlineexamhome.php on line 3
[this line was $u1=$_GET['username']

Notice: Undefined index: enrollno in M:xampphtdocsonlineexamhome.php on line 4

[this line was $e1=$_GET['enrollno'];
SORRY REGISTERED FIRST
CLICK HERE

Well, straight forward I can see something very wrong with your code: you didn't define any <head> tags, and you closed the <body> tag without opening it.

About the error, I just tried that exact same code and I had no problem. The only way that should give you trouble is if you try to access the home.php by itself, not through the form.

You get that notice because the GET array does not always contain that value. You can solve it by doing something like this:

$u1 = isset($_GET['username']) ? $_GET['username'] : '';
$e1 = isset($_GET['enrollno']) ? $_GET['enrollno'] : 0;

This way they always get a default value.

$u1 = isset($_GET['username']) ? $_GET['username'] : '';
$e1 = isset($_GET['enrollno']) ? $_GET['enrollno'] : 0;

great...my this arary problum is solve.. but can u plzz explne how its work what u wrt... and one prob is again ... come afetr registration.. the enrollnum and then user name not matched bcz its always give else output ..means registered first.. although i come after registation ..

$querry="select *from login where u_name='$u1',enrolled_no='e1'";

this is the query it has no problum but why its give again else value..