$cardCount = 10;
$arr = array();
for ($i = 1; $i <= $cardCount; $i++) {
$strCard = str_pad($i, 10, '0', STR_PAD_LEFT);
$arr[] = $strCard;
}

print_r($arr);

Array ( [0] => 0000000001 [1] => 0000000002 [2] => 0000000003 [3] => 0000000004 [4] => 0000000005

[5] =>0000000006 [6] => 0000000007 [7] => 0000000008 [8] => 0000000009 [9] => 0000000010 )