Datetime comparison PHP/Mysql?

Question

I'm trying to make something like this:

if (datetime - system date > 15 minutes) (false)

if (datetime - system date <= 15 minutes) (true)

But I'm totally lost. I don't know how to make this operation in PHP.

I'd like to see how I can pick that DateTime from my database and check if it's between the last 15 minutes of my server's time.

The type of database is MySQL.

---

Finally, I managed to do it thanks to Sammitch and the other ones, here i leave the snippet:

$now    = time();
$target = strtotime($row[1]);
$diff   = $now - $target;

// 15 minutes = 15*60 seconds = 900
if ($diff <= 900) {
    $seconds = $diff;
} else {
    $seconds = $diff;
}

Answer 1

If your dates are already in MySQL you will want to do the comparison in the query because:

1. MySQL has proper DATE types.
2. MySQL has indexes for comparison.
3. MySQL performs comparisons much faster than PHP.
4. If you filter your data in the query then less, or no time is spent transferring superfluous data back to the application.

Below is the most efficient form. If there is an index on the date column it will be used.

SELECT *
FROM table
WHERE date > DATE_SUB(NOW(), INTERVAL 15 MINUTE)

Docs: DATE_SUB()

If you need to do it in PHP:

$now = time();
$target = strtotime($date_from_db);
$diff = $now - $target;
if ( $diff > 900 ) {
  // something
}

or, more succinctly:

if( time() - strtotime($date_from_db) > 900 ) {
  // something
}