note 21864 added to function.is-numeric

I am using "is_numeric" to check a form variable to make sure the user has entered numbers. if (!is_numeric($isbn)){ $err .= print "ISBN must be numbers!"; } When ISBN is a non-numeric value, $err correctly contains "ISBN must be numbers" but is followed by a 1. Does anyone have an idea why this one is showing up? or what I can do to prevent it from printing? Thanks- Laura -- http://www.php.net/manual/en/function.is-numeric.php http://master.php.net/manage/user-notes.php?action=edit+21864 http://master.php.net/manage/user-notes.php?action=delete+21864 http://master.php.net/manage/user-notes.php?action=reject+21864