encrypteing variables that pass through url

[phprock]

Hi
I am tyring to encrypte variables because I dont want user anyone know the variabeles that pass through url.

let say i have variabels $id and $phone which pass through ..

index.php?file=user&id=121&phone=121

I want encrypte all these information
let say to

index.php?file=encryptefils
(ie.index.php?file=3424XCDFDfd545V)

Then i decrypte the $file variabls

what i want just some suggestions or coments on weather it i is good method or not.

Here is one example

<?

function index(){

//test variable that is sppose to be in the url
$old="var1|23|var2|2";

$new=encoded($old);

echo"Old :$old<hr> New:$new<hr><a href=$_SERVER[PHP_SELF]?op=link2&amp;sid=$new>Go to link2 where you decrypte the variables</a>";


}

function link2(){

echo"This is link 2. Go to <a href=$_SERVER[PHP_SELF]>home</a><hr>";
$decoded=decoded($_GET["sid"]);

echo"Decoded:$decode<hr>";

$array=array();
$array=explode("|","$decoded");

$var1=$array[1];
$var2=$array[3];


echo"Var1: $var1<br>Var 2: $var2";


}

// from php.net

function encoded($ses)
{
  $sesencoded = $ses;
  $num = mt_rand(3,9);
  for($i=1;$i<=$num;$i++)
  {
     $sesencoded =
     base64_encode($sesencoded);
  }
  $alpha_array =
  array('Y','D','U','R','P',
  'S','B','M','A','T','H');
  $sesencoded =
  $sesencoded."+".$alpha_array[$num];
  $sesencoded =
  base64_encode($sesencoded);
  return $sesencoded;
}//end of encoded function



// from php.net
function decoded($str)
{
   $alpha_array =
   array('Y','D','U','R','P',
   'S','B','M','A','T','H');
   $decoded =
   base64_decode($str);
   list($decoded,$letter) =
   split("\+",$decoded);
   for($i=0;$i<count($alpha_array);$i++)
   {
   if($alpha_array[$i] == $letter)
   break;
   }
   for($j=1;$j<=$i;$j++)
   {
     $decoded =
       base64_decode($decoded);
   }
   return $decoded;
}//end of decoded function


switch($_REQUEST["op"]){


default:
index();
break;

case"link2":
link2();
break;

}




?>