sort url

function alphaID($in, $to_num = false, $pad_up = false, $passKey = null)
{
  $index = "abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
  if ($passKey !== null)
  {
    /* Although this function's purpose is to just make the
    * ID short - and not so much secure,
    * with this patch by Simon Franz (http://blog.snaky.org/)
    * you can optionally supply a password to make it harder
    * to calculate the corresponding numeric ID */
    for ($n = 0; $n<strlen($index); $n++)
    {
      $i[] = substr( $index,$n ,1);
    }
    $passhash = hash('sha256',$passKey);
    $passhash = (strlen($passhash) < strlen($index)) ? hash('sha512',$passKey) : $passhash;
    for ($n=0; $n < strlen($index); $n++)
    {
      $p[] = substr($passhash, $n ,1);
    }
    array_multisort($p, SORT_DESC, $i);
    $index = implode($i);
  }
  $base = strlen($index);
  if ($to_num)
  {
    // Digital number <<-- alphabet letter code
    $in = strrev($in);
    $out = 0;
    $len = strlen($in) - 1;
    for ($t = 0; $t <= $len; $t++)
    {
      $bcpow = bcpow($base, $len - $t);
      $out  = $out + strpos($index, substr($in, $t, 1)) * $bcpow;
    }
    if (is_numeric($pad_up))
    {
      $pad_up--;
      if ($pad_up > 0)
      {
        $out -= pow($base, $pad_up);
      }
    }
    $out = sprintf('%F', $out);
    $out = substr($out, 0, strpos($out, '.'));
  }
  else
  {
    // Digital number -->> alphabet letter code
    if (is_numeric($pad_up))
    {
      $pad_up--;
      if ($pad_up > 0)
      {
        $in += pow($base, $pad_up);
      }
    }
    $out = "";
    for ($t = floor(log($in, $base)); $t >= 0; $t--)
    {
      $bcp = bcpow($base, $t);
      $a  = floor($in / $bcp) % $base;
      $out = $out . substr($index, $a, 1);
      $in = $in - ($a * $bcp);
    }
    $out = strrev($out); // reverse
  }
  return $out;
}
$r=rand();
echo $r."<br>";
$s=alphaID($r,false,false,'678%4@Ttuy');
echo $s."<br>";
echo alphaID($s,true,false,'678%4@Ttuy');