How to replace last 15 digits of a string with x?

Question

Let's say I've got a string which I want to display on my user's settings page. It's the HWID of the specific user but I want to hide like the last 15 characters from the string with x for example. How to do this ? Probably preg_replace() .. please let me know.

Example string: aaaec315bbfb9184fd9d7c8e165b297d but it will display like aaaec315bbfb9184f************** for exmaple

I believe it can only contain an alphanumeric characters since it's a HWID.

Answer 1

$string = substr($string,0,-15)."xxxxxxxxxxxxxxx";

Answer 2

While @hellocde's example does do this, I would just use the native substr_replace function instead as this is what it's intended for.

substr_replace($string, 'xxxxxxxxxxxxxx', -15);

Which will produce:

aaaec315bbfb9184fdxxxxxxxxxxxxxx

Functional example