Question

 <?php
 include 'db.php';
 $mail=$_SESSION['session_u_e_mail'];
if(!isset($_GET['edit']))
{
$_GET['edit']=0;
}
switch($_GET['edit'])
{
 case 1: echo "Value";
         break;

 case 2: echo "Value";
         break;

 default: echo "Value";
         break;

 }

I m facing problem that the values in every case is echoed twice.

Answer 1

There is nothing in this code that would even output your default value. No matter the input, this outputs Value. Look in db.php or the files included by it for debugging echoes.