驗證銀行卡位數和正確性 ``` 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'; } } ```