<?php
$a = new DateTime();
$b = new DateTime();
$c = new DateTime();
$arr = [
$a, $b, $c
];
foreach ($arr as $key => $value) {
echo $value->format('Y-m-d');
}
PD9waHAKCiRhID0gbmV3IERhdGVUaW1lKCk7CiRiID0gbmV3IERhdGVUaW1lKCk7CiRjID0gbmV3IERhdGVUaW1lKCk7CgokYXJyID0gWwoJJGEsICRiLCAkYwpdOwoKZm9yZWFjaCAoJGFyciBhcyAka2V5ID0+ICR2YWx1ZSkgewoJZWNobyAkdmFsdWUtPmZvcm1hdCgnWS1tLWQnKTsKfQ==