PHP我需要将一个逗号分隔的字符串拆分成一个数组，但是当逗号出现在数字之间时忽略它

$str = "1,2,3,4,5,6,7,8,9,10";
$array = explode(",", $str);
print_r($array);

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 5
    [5] => 6
    [6] => 7
    [7] => 8
    [8] => 9
    [9] => 10
)

$str = "1,2,3,4,5,6,7,8,9,10,11,12";
$array = explode(",", $str);
print_r($array);

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 5
    [5] => 6
    [6] => 7
    [7] => 8
    [8] => 9
    [9] => 10
    [10] => 11
    [11] => 12
)