How to format an UTC date to use the Z (Zulu) zone designator in php?

Question

I need to display and handle UTC dates in the following format:

2013-06-28T22:15:00Z

As this format is part of the ISO8601 stand

Answer 1

The Zulu time zone (Z) is exactly the same as Coordinated Universal Time (UTC). Interestingly, PHP recognizes "Z" as a valid timezone code although it's not listed among supported timezones.

That allows to leverage the built-in format character "T" that renders the timezone abbreviation dynamically instead of the hard-coded "Z" suffix.

$zulu = $date->setTimeZone(new \DateTimeZone('Z'));
echo $zulu->format('Y-m-d\TH:i:sT');
// 2020-05-20T21:09:48Z

The example assumes \DateTimeImmutable instance that gets cloned by the timezone setter while keeping the original instance intact.

UPDATE: Initially, the answer featured the built-in constant \DateTime::RFC3339 that relies on the format character "P" instead of the needed "T" making it not suitable. Admittedly, the solution has lost its appeal as it now requires to explicitly specify the format just like the alternatives.