note 124006 added to class.weakreference

I am using PHP 7.3.4-1+ubuntu18.04.1+deb.sury.org+3. Tried the code snippet in the document for WeakReference. $obj=new StdClass(); $weakref =WeakReference::create($obj); var_dump($weakref->get()); // unset($obj); var_dump($weakref->get()); OUTPUT ======= PHP Fatal error: Uncaught Error: Class 'WeakReference' not found in Command line code:1 Stack trace: #0 {main} thrown in Command line code on line 1 Fatal error: Uncaught Error: Class 'WeakReference' not found in Command line code:1 Stack trace: #0 {main} thrown in Command line code on line 1 ---- Server IP: 208.43.231.9 Probable Submitter: 82.199.157.34 (proxied: 117.254.36.114) ---- Manual Page -- http://php.net/manual/en/class.weakreference.php Edit -- https://master.php.net/note/edit/124006 Del: integrated -- https://master.php.net/note/delete/124006/integrated Del: useless -- https://master.php.net/note/delete/124006/useless Del: bad code -- https://master.php.net/note/delete/124006/bad+code Del: spam -- https://master.php.net/note/delete/124006/spam Del: non-english -- https://master.php.net/note/delete/124006/non-english Del: in docs -- https://master.php.net/note/delete/124006/in+docs Del: other reasons-- https://master.php.net/note/delete/124006 Reject -- https://master.php.net/note/reject/124006 Search -- https://master.php.net/manage/user-notes.php