I want to convert DOMTimeStamp from Geolocation in PHP in order to save it in DATETIME in the database. How can I accomplish this?
It's a just a timestamp in milliseconds. Just convert it to seconds and then use PHP's built in Date/Time functionality to convert it:
$timestamp = floor($domtimestamp / 1000); // Get seconds from milliseconds
$datetime = new DateTime('@'.$timestamp);
echo $datetime->format('Y-m-d H:i:s');