php hide credit card middle numbers

1$email = 'divakar.kumar6@gmail.com';
2$email =  substr_replace($email,"xxxxxxxxxx",3,10);
3
4$contact = "9899784414";
5$contact = substr_replace($contact,"xxxxxx",2,6);
6
7echo $email;
8echo "<br/>";
9echo $contact;
10