$days = array();
for ($i = 0; $i < 30; $i++) {
$days[] = date("d", strtotime('-'. $i .' days'));
}
print_r($days);
/*
run:
Array
(
[0] => 10
[1] => 09
[2] => 08
[3] => 07
[4] => 06
[5] => 05
[6] => 04
[7] => 03
[8] => 02
[9] => 01
[10] => 31
[11] => 30
[12] => 29
[13] => 28
[14] => 27
[15] => 26
[16] => 25
[17] => 24
[18] => 23
[19] => 22
[20] => 21
[21] => 20
[22] => 19
[23] => 18
[24] => 17
[25] => 16
[26] => 15
[27] => 14
[28] => 13
[29] => 12
)
*/