Null Coalescing Assignment Operator examples. Try it now : https://3v4l.org/pV6PF

gist.php

<?php
# Null Coalescing Assignment Operator

# OLD WAY (PHP < 7.4 )
$data['comments']['user_id'] = $data['comments']['user_id'] ?? 'PlaceHoldered value...';
var_dump($data['comments']['user_id']);
$data = null;

# PHP 7.4 + syntax to use new assigment operator without unecessary tests.
$data['comments']['user_id'] ??= 'PlaceHoldered value...';
var_dump($data['comments']['user_id']);