Adding time to time saved in mysql through PHP - php

Question

I'm a very rookie programmer when it comes to PHP. I can usually manage most problems that I run into, but with this one I'm stumped.
I'm trying to create a program where a user can insert a name into a table, and 30 minutes after insertion the name would be flagged as "expired". I'm able to create the row in MySql and using MySql I can put the time when the name was entered. Now what I'm trying to do is take that time from the database and check if it's been 30 minutes since it was entered.
I figure I could do this by taking the time from the database, adding 30 minutes to it, then checking against the current time to see if its past it yet.
This is what I have so far. The time is in this format: 2013-08-21 13:18:35
$result = mysqli_query($con,"SELECT * FROM list ORDER BY id desc");
//snip snip
while($row = mysqli_fetch_array($result))
{
echo "<tr>";
echo "<td>" . $row['id'] . "</td>";
echo "<td>" . $row['username'] . "</td>";
echo "<td>" . $row['reason'] . "</td>";
echo "<td>" . $row['date'] . "</td>";
cho "</tr>";
}
Now I know that I need to take $row['date'] and add 30 minutes to it. I've read probably about 20 different pages about this, but nothing I do seems to work.
I've seen a few different things suggest such as date_add() and strtotime but either I'm doing something wrong, or it doesn't work.
If I could just get a working code sample for how to add 30 minutes to $row['date'], I'm sure I could explain it to myself.
I know how to compare the two once I've got the 30 minutes added, and I think this would be correct:
if ($time30 < $now) {
// Code to execute
}
Any help would be appreciated.

Answer 1

Considering that $row['date'] prints out 2013-08-21 13:18:35. you need to use strtotime() to convert that value into a timestamp.
See documentation here strtotime.
Now that you have a timestamp, you simply add 1800 seconds to it (half an hour) and you obtain what you need.
Then, a simple comparison between your time and now (you obtain the value with time() ) will give you the result.
This code is a mere example (even too much detailed, because it can be shorter):
$db_time = strtotime("2013-08-21 20:18:35");
$half_hour = 1800;
$time = $db_time + $half_hour;
if($time < time()) echo "expired"; else echo "active";

Answer 2

First, avoid select *
Mysql solution would be to return the time after 30 mins as a column
SELECT TIMESTAMPADD(MINUTE,30,date1);
Assuming date1 is your column name avoid using date as a column name, at best its a maintenance issue

Answer 3

In PHP:
$time30 = strtotime($row['date']) + (30 * 60);
$now = time();
In MySQL
SELECT *,timestampadd(minute,30,date)<now() as expired FROM list ORDER BY id DESC
Then in the PHP you have $row['expired'] as a 1 or 0.