[PHP-BUG] Req #71254 [NEW]: Allow limited recursion with __get().

From:             andreas at dqxtech dot net
Operating system: 
PHP version:      7.0.2RC1
Package:          Class/Object related
Bug Type:         Feature/Change Request
Bug description:Allow limited recursion with __get().

Description:
------------
Currently, magic __get() refuses to dive into recursion if the same key
is repeated.
https://3v4l.org/00Kuv

It stops, and gives a "Notice: Undefined property: C::$x".

There are cases where the recursion is not a bug, and it is indeed
legitimate to dive one level into the recursion.

As we can see, calling ->__get('x') explicitly instead of magic ->x,
avoids the notice. But this is undesirable, because we want the IDE to
recognize that we are calling @property $x.

The unlimited recursion can be avoided with stubs:
https://3v4l.org/Nb3VF

Proposal:
I want to propose that the recursion detection mechanic only gets active
if the same key is used a 3rd time, not the 2nd time. This permits the
legitimate case, but still prevents unlimited recursion.

Test script:
---------------

<?php
class C {
    private $buffer = array();
    function __get($key) {
        if (array_key_exists($key, $this->buffer)) {
            return $this->buffer[$key];
        }
        $f = 'calc_' . $key;
        return $this->buffer[$key] = $this->$f();
    }
    function calc_x() {
        $x = new stdClass;
        // Set a stub to avoid infinite recursion.
        $this->buffer['x'] = $x;
        $x->y = $this->y;
        return $x;
    }
    function calc_y() {
        $y = new stdClass;
        // Set a stub to avoid infinite recursion.
        $this->buffer['y'] = $y;
        $y->x = $this->x;
        return $y;
    }
}


-- 
Edit bug report at https://bugs.php.net/bug.php?id=71254&edit=1
-- 
Try a snapshot (PHP 5.4):   https://bugs.php.net/fix.php?id=71254&r=trysnapshot54
Try a snapshot (PHP 5.5):   https://bugs.php.net/fix.php?id=71254&r=trysnapshot55
Try a snapshot (trunk):     https://bugs.php.net/fix.php?id=71254&r=trysnapshottrunk
Fixed in SVN:               https://bugs.php.net/fix.php?id=71254&r=fixed
Fixed in release:           https://bugs.php.net/fix.php?id=71254&r=alreadyfixed
Need backtrace:             https://bugs.php.net/fix.php?id=71254&r=needtrace
Need Reproduce Script:      https://bugs.php.net/fix.php?id=71254&r=needscript
Try newer version:          https://bugs.php.net/fix.php?id=71254&r=oldversion
Not developer issue:        https://bugs.php.net/fix.php?id=71254&r=support
Expected behavior:          https://bugs.php.net/fix.php?id=71254&r=notwrong
Not enough info:            https://bugs.php.net/fix.php?id=71254&r=notenoughinfo
Submitted twice:            https://bugs.php.net/fix.php?id=71254&r=submittedtwice
register_globals:           https://bugs.php.net/fix.php?id=71254&r=globals
PHP 4 support discontinued: https://bugs.php.net/fix.php?id=71254&r=php4
Daylight Savings:           https://bugs.php.net/fix.php?id=71254&r=dst
IIS Stability:              https://bugs.php.net/fix.php?id=71254&r=isapi
Install GNU Sed:            https://bugs.php.net/fix.php?id=71254&r=gnused
Floating point limitations: https://bugs.php.net/fix.php?id=71254&r=float
No Zend Extensions:         https://bugs.php.net/fix.php?id=71254&r=nozend
MySQL Configuration Error:  https://bugs.php.net/fix.php?id=71254&r=mysqlcfg