/includes/assign.php

<? 	if ($_SESSION['logged_in'] != true) {
	echo "There has been an error, please go back and try again";
	die();
}
	$return = escape($_POST['return']);
	$shift = escape($_POST['id']);
	$c_user = escape($_POST['c_id']);
	//check to see if shift is in the past
	$r = mysql_query("SELECT * FROM hours WHERE id='$shift'");
	$r = mysql_fetch_array($r);
	$str = "$r[3]-$r[2]-$r[1]"; //get the date of the shift
	$shift_date = strtotime($str);
	if (time() > $shift_date) { 
		echo "You cannot edit shifts that are in the past, redirecting...";
		echo "<META HTTP-EQUIV='Refresh' Content='1; URL=index.php?page=cal&$return'>";
		die();
	}
	mysql_query("UPDATE hours SET worker='$c_user' WHERE id='$shift'");
	echo "<META HTTP-EQUIV='Refresh' Content='0; URL=index.php?page=cal&$return'>";