Easy Regex question

Trying to replace the first 12 digits of credit card numbers with X's in a predictable blob of text that contains the string:

Credit Card Number: 1234123412341234

Here's my PHP function:

preg_replace('/Credit Card Number: ([0-9]{12})/','Cred开发者_开发问答it Card Number: XXXXXXXXXXXX',$str);

Help?

I don't see what's wrong. Perhaps you forgot to assign the result?

$str = preg_replace('/Credit Card Number: [0-9]{12}/','Credit Card Number: XXXXXXXXXXXX',$str);

Also, the capturing around ([0-9]{12}) is unnecessary if you don't need it.

Dumb question: you are assigning the returned value back to $str right?

$str = preg_replace('/(Credit Card Number: [0-9]{12}/','Credit Card Number: XXXXXXXXXXXX',$str);