银行卡号验证是否正确 PHP

废话不多说，已亲测可用，直接上函数代码：

public function check_bankCard($card_number){        $arr_no = str_split($card_number);        $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;        $x = 10 - ($total % 10);        if($x == $last_n){            return 'true';        }else{            return 'false';        }    }