In addition to what was mentioned already, using ereg_replace, if you're pulling the CC# string out of a database of off of some POST data or something, just use a substr() function to pull the last 4 digits and prepend a bunch of X's. $ccnum = "342342522342342"; # fake CC #, prob not even correct # of digits :) $maskedccnum = "XXXXXXXXXXX" . substr($ccnum,strlen($ccnum)-5,4); If you're trying to do it in a form, realtime as the user enters it, you'd have to use some funky javascript or do something with a password form type or something. But sounds like you want it like when you display an invoice afterwards or display a "Would you like to use this CC that's already on file?" type thing without exposing the whole CC#. -TG = = = Original message = = = Hello, I need to replace all the numbers of a credit card except for the last 4 with an 'X' ... can't seem to locate the string function for this... can someone point me in the right direction here to what php item i should be using. Thanks! Joe ___________________________________________________________ Sent by ePrompter, the premier email notification software. Free download at http://www.ePrompter.com. -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php