note 129345 added to function.preg-replace

You can only use numeric backreferences in the replacement string, but not named ones: <?php echo preg_replace('#(\d+)#', '\1 $1 ${1}', '123'); // 123 123 123 echo preg_replace('#(?<digits>\d+)#', '\digits $digits ${digits}', '123'); // \digits $digits ${digits} ?> To use named backreferences, you have to use preg_replace_callback: <?php echo preg_replace_callback('#(?<digits>\d+)#', function( $m ){ return "$m[1] $m[digits] {$m['digits']}"; }, '123'); // 123 123 123 echo preg_replace_callback('#(?<digits>\d+)#', fn($m) => "$m[1] $m[digits] {$m['digits']}", '123'); // 123 123 123 ?> See https://bugs.php.net/bug.php?id=81469 ---- Server IP: 45.112.84.4 Probable Submitter: 80.90.13.131 (proxied: 84.236.79.56) ---- Manual Page -- https://php.net/manual/en/function.preg-replace.php Edit -- https://main.php.net/note/edit/129345 Del: integrated -- https://main.php.net/note/delete/129345/integrated Del: useless -- https://main.php.net/note/delete/129345/useless Del: bad code -- https://main.php.net/note/delete/129345/bad+code Del: spam -- https://main.php.net/note/delete/129345/spam Del: non-english -- https://main.php.net/note/delete/129345/non-english Del: in docs -- https://main.php.net/note/delete/129345/in+docs Del: other reasons-- https://main.php.net/note/delete/129345 Reject -- https://main.php.net/note/reject/129345 Search -- https://main.php.net/manage/user-notes.php