When using php sessions with a registered array variable; if that variable is set before the call to session_start() is made, instead of overwriting the variable with the stored session value I request php check if that variable is already set and do an array_merge() on the two arrays. This is useful for accumulating key and value pairs.

Example

first..

<? 
$input = array();
session_register("input");
?>

then..

<?

// Upon form submission at session_start() the input variable is overwritten
session_start();

var_dump($input);

?>

<form>
<input type="text" name="input[<?echo time()?>]">
<input type="submit">
</form>