Using $_POST data to create a new html form value - php

Question

I'm using post to send info to my page. I'm using that to create a variable and pass that variable to a new <input>. However, when I submit the new form, the variable is blank.
The variable is created from post data:
$timenotstarted = $_POST["placeholder"];
Then inline in the html:
<form name="newform" method="post" action="insert.php">
<input type="text" name="timerset" value="<?php echo $timenotstarted; ?>">
<input type="submit" value="Submit"><
</form>
When the new form is submitted, the variable whose name="timerset", is blank.
When I echo $timenotstarted on the same page that this form is,
it will show its value. It just "goes away" when I try to use it in the new form.
Edit: Here's what's happeneing:
Not sure if this helps: http://forexguruguide.com/timer/insert.php
And here's the whole shabang:
<?php include 'connect.php';
$timenotstarted = $_GET["placeholder"];
$start = $_POST["start"];
$timerset = $_post["timerset"];
echo $timenotstarted . '<br />';
echo $start . '<br />';
echo $timerset . '<br />';
?>
<form name="timeform" method="get" action="insert.php">
<select name="placeholder">
<option value="1">1 min</option>
<option value="3">3 min</option>
<option value="5">5 min</option>
<option value="10">10 min</option>
</select>
<input type="submit" value="Set timer">
</form>
<form name="startform" method="post" action="insert.php">
<input type="hidden" value="1" name="start">
Timer set to: <input type="text" name="timerset" value="<?php print $timenotstarted?>">
<input type="Submit" value="Start Timer">
</form>
<?php
if ($start==1) {
$target = time() + ($timerset * 60);
mysql_query("UPDATE countdowntimer SET target='$target' WHERE id='0'");
mysql_query("UPDATE countdowntimer SET timenotstarted='null' WHERE id='0'");
echo 'Timer started' . '<br />';
echo $target . '<br />';
echo time(); }
else if (!empty($timenotstarted)) {
$timenotstarted .= ":00";
mysql_query("UPDATE countdowntimer SET timenotstarted='$timenotstarted'");
echo 'Timer set to: ' . $timenotstarted; }
else {
echo 'Set the timer then start the timer'; }
?>

Answer 1

shouldn't use POST for that. It's GET's job
<? if (!isset($_GET['placeholder'])): ?>
<form>
Enter placeholder:
<input type="text" name="placeholder" value="">
<input type="submit" value="Submit">
</form>
<? else: ?>
<form name="newform" method="post" action="insert.php">
<input type="text" name="timerset" value="<?=htmlspecialchers($_GET["placeholder"])?>">
<input type="submit" value="Submit">
</form>
<? endif ?>

Answer 2

It's not clear to me what you're doing wrong from your post, but here's the basics on how to do it right:
page1.php
<form action="page2.php" method="post">
<input type="hidden" name="foo" value="bar"/>
<input type="submit"/>
</form>
page2.php
<form>
<input name="foo2" value="<?php echo htmlspecialchars($_POST['foo']); ?>"/>
</form>

Answer 3

So, here's what FINALLY worked. I just rebuilt the second form...:
<form name="testyboy" method="post" action="insert.php">
<input type="hidden" value="1" name="start">
<input type="hidden" value="<?php print $timenotstarted?>" name="testyboy">
<input type="submit" value="Start Timer">
</form>
It's identical. I have no idea what made it work....
Anyways thanks for everyone's efforts! Its much appreciated.