function 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;
}
}
