Формирование массива, содержащий все часы из интервала

$period = new DatePeriod(
	 new DateTime('09:00'),
	 new DateInterval('PT1H'),
	 new DateTime('18:01')
);

$dates = array();
foreach ($period as $key => $value) {
	$dates[] = $value->format('H:00');     
}

print_r($dates);

Результат:

Array
(
    [0] => 09:00
    [1] => 10:00
    [2] => 11:00
    [3] => 12:00
    [4] => 13:00
    [5] => 14:00
    [6] => 15:00
    [7] => 16:00
    [8] => 17:00
    [9] => 18:00
)

Интервал с шагом в 30 минут

$period = new DatePeriod(
	 new DateTime('09:00'),
	 new DateInterval('PT30M'),
	 new DateTime('18:01')
);

$dates = array();
foreach ($period as $key => $value) {
	$dates[] = $value->format('H:i');     
}

print_r($dates);

Результат:

Array
(
    [0] => 09:00
    [1] => 09:30
    [2] => 10:00
    [3] => 10:30
    [4] => 11:00
    [5] => 11:30
    [6] => 12:00
    [7] => 12:30
    [8] => 13:00
    [9] => 13:30
    [10] => 14:00
    [11] => 14:30
    [12] => 15:00
    [13] => 15:30
    [14] => 16:00
    [15] => 16:30
    [16] => 17:00
    [17] => 17:30
    [18] => 18:00
)

$period = new DatePeriod(
	 new DateTime('28.03.2022 18:00'),
	 new DateInterval('PT1H'),
	 new DateTime('29.03.2022 09:01')
);

$dates = array();
foreach ($period as $key => $value) {
	$dates[] = $value->format('d.m.Y H:00');     
}

print_r($dates);

Результат:

Array
(
    [0] => 28.03.2022 18:00
    [1] => 28.03.2022 19:00
    [2] => 28.03.2022 20:00
    [3] => 28.03.2022 21:00
    [4] => 28.03.2022 22:00
    [5] => 28.03.2022 23:00
    [6] => 29.03.2022 00:00
    [7] => 29.03.2022 01:00
    [8] => 29.03.2022 02:00
    [9] => 29.03.2022 03:00
    [10] => 29.03.2022 04:00
    [11] => 29.03.2022 05:00
    [12] => 29.03.2022 06:00
    [13] => 29.03.2022 07:00
    [14] => 29.03.2022 08:00
    [15] => 29.03.2022 09:00
)