function getLastNDays($days, $format = 'd-m-Y'){
    $m = date("m"); $de = date("d")-1; $y= date("Y");
    $dateArray = array();
    for($i=0; $i<=$days-1; $i++){

        $dateArray[] = date($format, mktime(0,0,0,$m,($de-$i),$y));
    }
    $dateArray[] = 'x';
    return array_reverse($dateArray);
}

$sevenarr = getLastNDays(30);

Array
(
    [0] => x
    [1] => 19-06-2018
    [2] => 20-06-2018
    [3] => 21-06-2018
    [4] => 22-06-2018
    [5] => 23-06-2018
    [6] => 24-06-2018
    [7] => 25-06-2018
    [8] => 26-06-2018
    [9] => 27-06-2018
    [10] => 28-06-2018
    [11] => 29-06-2018
    [12] => 30-06-2018
    [13] => 01-07-2018
    [14] => 02-07-2018
    [15] => 03-07-2018
    [16] => 04-07-2018
    [17] => 05-07-2018
    [18] => 06-07-2018
    [19] => 07-07-2018
    [20] => 08-07-2018
    [21] => 09-07-2018
    [22] => 10-07-2018
    [23] => 11-07-2018
    [24] => 12-07-2018
    [25] => 13-07-2018
    [26] => 14-07-2018
    [27] => 15-07-2018
    [28] => 16-07-2018
    [29] => 17-07-2018
    [30] => 18-07-2018
)