How to group the datetime values of a flat array by date?

I have an array that list datetime. How to group the array that has the same date.

$array = [
   "2019-07-17 10:02:00",
   "2019-07-17 12:00:00",
   "2019-07-18 08:00:00",
   "2019-07-19 01:00:00",
   "2019-07-19 02:00:00"
];

Expected result :

$result = [
       0 => [
            "2019-07-17 10:02:00",
            "2019-07-17 12:00:00"
       ],
      1 => [
            "2019-07-18 08:00:00"
       ],
       2 => [
            "2019-07-19 01:00:00",
            "2019-07-19 02:00:00"
       ]
];

Try this:

$grouped = [];
foreach ($array as $dateString) {
    $dateObject = new \DateTime($dateString);
    $grouped[$dateObject->format('Y-m-d')][] = $dateString;
}
$grouped = array_values($grouped);
var_dump($grouped);

Example.