- print_r: documentation ( source)
<?php
$array = [['range' => 336, 'year' => 2020],['range' => 336, 'year' => 2020],['range' => 390, 'year' => 2020],['range' => 390, 'year' => 2021]];
$newDatesCurrent = [];
foreach($array as $value) {
$newDatesCurrent[] = ['range' => $value['range'], 'year' => $value['year'], 'month' => 222];
}
print_r($newDatesCurrent);