php如何返回值为000001而不是1?

Question

EG: 固定6位长度, 000001, 000002, 000003,......

依次增长.

Answer 1

str_pad($number, 6, '0', STR_PAD_LEFT);

Answer 2

sprintf("%06d", $num);

Answer 3

    echo sprintf("%'06d\n", 1);

Answer 4

sprintf("%06d", $num);