<?php
if ($_POST['submit'] && $_POST['leap']){
$leapy = $_POST['leap'];
?>
<form method="post" action="populate2.php">
A leap year occurs every 
<SELECT NAME="leap">
<OPTION>
<?
if ($leapy!="" && $leapy!="Select number") {
print $leapy;
print ("<option value=\"Select number\">Select number");
} else {
print ("Select number");}
?>
<option value="1">1
<option value="2">2
<option value="3">3
<option value="4">4
<option value="5">5
<option value="6">6
<option value="7">7
</SELECT> years.
<input type="submit" name="submit" value="submit">
<form>
<?
}else{
?>
<form method="post" action="populate2.php">
A leap year occurs every 
<SELECT NAME="leap">
<OPTION>Select number
<option value="1">1
<option value="2">2
<option value="3">3
<option value="4">4
<option value="5">5
<option value="6">6
<option value="7">7
</SELECT> years.
<input type="submit" name="submit" value="submit">
<form>
<?
}
?>