note 112352 added to regexp.reference.assertions

An example of replacing all but the first four and last four characters of a string (or digits of a credit card number): preg_replace('/(?<!^|^.|^..|^...).(?!.{0,3}$)/', '*', '1234567890123456'); // 1234********3456 Notice how the lookbehind requires a non-nested fixed-width expression, while the lookahead is OK with the {0,3} varied width. ---- Server IP: 69.147.83.199 Probable Submitter: 204.62.150.2 ---- Manual Page -- http://php.net/manual/en/regexp.reference.assertions.php Edit -- https://master.php.net/note/edit/112352 Del: integrated -- https://master.php.net/note/delete/112352/integrated Del: useless -- https://master.php.net/note/delete/112352/useless Del: bad code -- https://master.php.net/note/delete/112352/bad+code Del: spam -- https://master.php.net/note/delete/112352/spam Del: non-english -- https://master.php.net/note/delete/112352/non-english Del: in docs -- https://master.php.net/note/delete/112352/in+docs Del: other reasons-- https://master.php.net/note/delete/112352 Reject -- https://master.php.net/note/reject/112352 Search -- https://master.php.net/manage/user-notes.php