is date_create in php internet time or system time code example

Example 1: php time

<?php
$t=time();
echo($t . "<br>");
echo(date("Y-m-d",$t));
?>

Example 2: how to set date in php

// 1. create a date instance
$date = new DateTime;

// 2. set the date using the setDate(year, month, date) method on the
//    $date instance
$date->setDate(1999,02,19);

Example 3: php date

$dateTime = new \DateTime();
/**
 * You can get the string by using format
 */
$dateTime->format('Y-m-d H:i:s');