ErrorException: Creation of dynamic property Page::$id is deprecated

Debugger::handle_error (8192, "Creation of dynamic property Page::$id is deprecated", "/home/semplia/www/cli/aimeonlus/apps/admin/handlers/page.php", 76)

76/home/semplia/www/cli/aimeonlus/apps/admin/handlers/page.php

74.

<?php 
75.
<?php // set the page properties
76.
<?php $page->id = $id;
77.
<?php $page->title = Template::sanitize ($wp->title);
78.
<?php $page->_menu_title = Template::sanitize ($wp->menu_title);

require ("/home/semplia/www/cli/aimeonlus/apps/admin/handlers/page.php")

516/home/semplia/www/cli/aimeonlus/lib/Controller.php

514.

<?php         // Run the handler and get its output
515.
<?php         ob_start ();
516.
<?php         $res = require ($handler);
517.
<?php         $out = ob_get_clean ();
518.
<?php         if (is_string ($res) && strlen ($res) > 0) {

Controller->handle ("apps/admin/handlers/page.php", false)

216/home/semplia/www/cli/aimeonlus/lib/FrontController.php

214.

<?php             $handler = $controller->route ($_SERVER['REQUEST_URI']);
215.
<?php         }
216.
<?php         $page->body = $controller->handle ($handler, false);
217.
<?php 
218.
<?php         /**

FrontController::run ()

34/home/semplia/www/cli/aimeonlus/index.php

32.

<?php $argc = isset ($argc) ? $argc : null;
33.
<?php $argv = isset ($argv) ? $argv : null;
34.
<?php return FrontController::run ($argv, $argc);


Fatal error: Uncaught ErrorException: Undefined array key 4 in /home/semplia/www/cli/aimeonlus/lib/Debugger.php:125 Stack trace: #0 /home/semplia/www/cli/aimeonlus/lib/Debugger.php(125): Debugger::handle_error(2, 'Undefined array...', '/home/semplia/w...', 125) #1 /home/semplia/www/cli/aimeonlus/lib/Debugger.php(85): Debugger::show_trace(Array) #2 [internal function]: Debugger::handle_exception(Object(ErrorException)) #3 {main} thrown in /home/semplia/www/cli/aimeonlus/lib/Debugger.php on line 125