note 125720 added to regexp.reference.back-references

Mind that back references only work in single-quoted strings. In double quoted strings, they will be parsed as the octal notation of a character. <?php preg_match("/^(a)(?!\1)/", "aa"); // true, that's not what we want! // Notice the only difference being the single quotes. preg_match('/^(a)(?!\1)/', "aa"); // false ?> ---- Server IP: 45.112.84.4 Probable Submitter: 45.91.159.166 (proxied: 80.151.39.220) ---- Manual Page -- http://php.net/manual/en/regexp.reference.back-references.php Edit -- https://master.php.net/note/edit/125720 Del: integrated -- https://master.php.net/note/delete/125720/integrated Del: useless -- https://master.php.net/note/delete/125720/useless Del: bad code -- https://master.php.net/note/delete/125720/bad+code Del: spam -- https://master.php.net/note/delete/125720/spam Del: non-english -- https://master.php.net/note/delete/125720/non-english Del: in docs -- https://master.php.net/note/delete/125720/in+docs Del: other reasons-- https://master.php.net/note/delete/125720 Reject -- https://master.php.net/note/reject/125720 Search -- https://master.php.net/manage/user-notes.php