Replace all but last 4 digits in a string

[CRichardson]

I have a variable containing a string of digits, I would like to replace every digit but the last 4 with a star (*). How would I do it?
Chris.

[Weedpacket]

Use [man]substr[/man] to extract all but the last four characters. Then append "****" to the result.

[NogDog]

One possible solution:

$starred = substr_replace($number, str_repeat('*', strlen($number) - 4), 0, -4);