How to display a date as iso 8601 format with PHP

UNIX timestamp is the second argument of date,

We have to convert the database timestamp to strtotime() function.

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

The  DateTime class  can be used for display a date as iso 8601 format with PHP. It is available in the  PHP version 5.2 and later.

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

If we have PHP 5.4 , achieve this simple one liner.

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

Here is the easy and better function 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';
}