- var_dump: documentation ( source)
<?php
$string = '2018-01-11T15:36:16.000+01:00';
$date = new DateTime($string);
$datetime = new DateTimeImmutable($string);
$otherString = $date->format(DateTime::RFC3339_EXTENDED);
$immutableString = $datetime->format(DateTime::RFC3339_EXTENDED);
var_dump(
$string == $otherString,
$string == $immutableString,
DateTimeImmutable::getLastErrors()
);