public static function check_card($no)    {        $return = false;        $arr_no = str_split($no);        $last_n = $arr_no[count($arr_no)-1];        krsort($arr_no);        $i = 1;        $total = 0;        foreach ($arr_no as $n){            if($i%2==0){                $ix = $n*2;                if($ix>=10){                    $nx = 1 + ($ix % 10);                    $total += $nx;                }else{                    $total += $ix;                }            }else{                $total += $n;            }            $i++;        }        $total -= $last_n;        $total *= 9;        if($last_n == ($total%10)){            $return = true;        }       // var_dump($return);        return $return;    }

这里验证的前提需要保证银行卡号不能为空和0