Split string into pieces for output

[jfaust97]

Easiest example of what I am trying to do is this:

I am collecting a Credit Card number...
I want to display it on the receipt in the format of

1234-1234-1234-5678

Though it may have been entered as:

1234123412345678

So how do I tell PHP to count every 4th character and them insert a dash?

Thanks
Jeremy

[devinemke]

$string = '1234123412345678';
echo wordwrap($string, 4, '-', 1);