Stop False Array Values

[Dysan]

How do I stop the user from entering this php file manually, and accidentally adding a blank id to the array?

<?php
session_start();
$array = ( isset($_SESSION['ids']) && is_array($_SESSION['ids']) ) ?  $_SESSION['ids'] : array();

if (!in_array($_GET['id'], $array))
{
 $array[] = $_GET['id'];
}
else
{
  echo "ID Exists";
}
$_SESSION['ids'] = $array;
print_r($array);

?>

[bradgrafelman]

Use [man]empty/man to see if $_GET['id'] is empty or not (which you should be doing anyway, else you're generating notices due to sloppy coding).