How to display a date as iso 8601 format with PHP

I'm trying to display a datetime from my MySQL database as an iso 8601 formated string with PHP but it's coming out wrong.

17 Oct 2008 is coming out as: 1969-12-31T18:33:28-06:00 which is clearly not correct (the year should be 2008 not 1969)

This is the code I'm using:

<?= date("c", $post[3]) ?>

$post[3] is the datetime (CURRENT_TIMESTAMP) from my MySQL database.

Any ideas what's going wrong?

The second argument of date is a UNIX timestamp, not a database timestamp string.

You need to convert your database timestamp with strtotime.

<?= date("c", strtotime($post[3])) ?>

Using the DateTime class available in PHP version 5.2 it would be done like this:

$datetime = new DateTime('17 Oct 2008');
echo $datetime->format('c');

As of PHP 5.4 you can do this as a one-liner:

echo (new DateTime('17 Oct 2008'))->format('c');

###Procedural style :

echo date_format(date_create('17 Oct 2008'), 'c');
// Output : 2008-10-17T00:00:00+02:00

###Object oriented style :

$formatteddate = new DateTime('17 Oct 2008');
echo $datetime->format('c');
// Output : 2008-10-17T00:00:00+02:00

###Hybrid 1 :

echo date_format(new DateTime('17 Oct 2008'), 'c');
// Output : 2008-10-17T00:00:00+02:00

###Hybrid 2 :

echo date_create('17 Oct 2008')->format('c');
// Output : 2008-10-17T00:00:00+02:00

---

###Notes :

1. You could also use 'Y-m-d\TH:i:sP' as an alternative to 'c' for your format.

2. The default time zone of your input is the time zone of your server. If you want the input to be for a different time zone, you need to set your time zone explicitly. This will also impact your output, however :

   echo date_format(date_create('17 Oct 2008 +0800'), 'c'); // Output : 2008-10-17T00:00:00+08:00

3. If you want the output to be for a time zone different from that of your input, you can set your time zone explicitly :

   echo date_format(date_create('17 Oct 2008')->setTimezone(new DateTimeZone('America/New_York')), 'c'); // Output : 2008-10-16T18:00:00-04:00

For pre PHP 5:

function iso8601($time=false) {
	if(!$time) $time=time();
	return date("Y-m-d", $time) . 'T' . date("H:i:s", $time) .'+00:00';
}

Here is the good function for pre PHP 5: I added GMT difference at the end, it's not hardcoded.

function iso8601($time=false) {
    if ($time === false) $time = time();
    $date = date('Y-m-d\TH:i:sO', $time);
    return (substr($date, 0, strlen($date)-2).':'.substr($date, -2));
}

The problem many times occurs with the milliseconds and final microseconds that many times are in 4 or 8 finals. To convert the DATE to ISO 8601 "date(DATE_ISO8601)" these are one of the solutions that works for me:

// In this form it leaves the date as it is without taking the current date as a reference
$dt = new DateTime();
echo $dt->format('Y-m-d\TH:i:s.').substr($dt->format('u'),0,3).'Z';
// return-> 2020-05-14T13:35:55.191Z

// In this form it takes the reference of the current date
echo date('Y-m-d\TH:i:s'.substr((string)microtime(), 1, 4).'\Z');
return-> 2020-05-14T13:35:55.191Z

// Various examples:
$date_in = '2020-05-25 22:12 03.056';
$dt = new DateTime($date_in);
echo $dt->format('Y-m-d\TH:i:s.').substr($dt->format('u'),0,3).'Z';
// return-> 2020-05-25T22:12:03.056Z

//In this form it takes the reference of the current date
echo date('Y-m-d\TH:i:s'.substr((string)microtime(), 1, 4).'\Z',strtotime($date_in));
// return-> 2020-05-25T14:22:05.188Z