Adding expiry time when posting a record. Can you take a look at this?

[man5 0]

Basically what I am trying to do is have an option of choosing an "expiry time" when inserting a record.  I will then use that expiry time to make a countdown clock that will expire the record when reached 0; but that's the step after.  Right now I am having a bit of issue inserting that expiry time into the database.  Here is my code. 

 

The error i get in the option value is something like <option value="<b>Notice</b>:  Undefined variable...">.

<?php

$date_added			 =	date('Y-m-d H:i:s');

$expiry_1			 =	date('Y-m-d H:i:s', strtotime('$date_added + 1 hour'));
$expiry_6			 =	date('Y-m-d H:i:s', strtotime('$date_added + 6 hours'));
$expiry_12			 =	date('Y-m-d H:i:s', strtotime('$date_added + 12 hours'));

?>

<fieldset>
	<label>Expiry Time</label>												
	<select name="expiry_time">
		<option value="0">Select Time</option>
		<option value="<?php echo $expiry_1; ?>">1 hour</option>
		<option value="<?php echo $expiry_6; ?>">6 hours</option>
		<option value="<?php echo $expiry_12; ?>">12 hours</option>
	</select>
</fieldset>

[man5 0]

Nevermind.  I figured out the problem.  Basically the variables($expiry_1..etc) were only called when the form was submitted.  So I brought them outside of isset and now I get no errors.  But now I see another issue.  The hours are not being added to the date.  I get the same date for all 3. Can you tell me if my variables are correct?

[man5 0]

Alright so I have finally solved my issue.  My code in the original post is all correct, except instead of using single quotation( ' ) in the dates variables, I had to use double quotation( " ).  Now it shows the dates with added hours.

[Barand 1,569]

Alternatively (where $hours is 1, 6 or 12),

INSERT INTO mytable (date_added, expire_date) VALUES (NOW(), NOW()+INTERVAL $hours HOUR);