我用md5编写了一个随机代码,但是如何使代码仅包含数字
$this->db->select('RIGHT(service.tracking_number,4) as kode',FALSE);
$this->db->order_by('id_service','DESC');
$this->db->limit(1);
$query = $this->db->get('service');
if($query->num_rows() <> 0){
$data = $query->row();
$kode = intval($data->kode) + 1;
}else {
$kode = 1;
}
$kodemax = str_pad($kode,1,"0",STR_PAD_LEFT);
$kodejadi = "RJC".md5($kodemax);
$hasil = substr($kodejadi,-15);
return $hasil;
output RJC1679091c5a880faf6
如何制作这些输出数字?