Description:
------------
When called from inside a class method, $this->foo += 2 does not increment the variable.

$this->foo = $this->foo + 2 appears to work, though.

This looks related to bug 27798.

Reproduce code:
---------------
<?php

class foo {
    var $bar = 1;

    function baz() {
        $this->bar += 2;
        var_dump($this->bar);
        var_dump(get_object_vars($this));
    }
}

$f = new foo();
$f->baz();

$f->bar += 4;
var_dump($f->bar);

?>

Expected result:
----------------
int(3)
array(1) {
  ["bar"]=>
  int(3)
}
int(7)


Actual result:
--------------
int(1)
array(2) {
  ["bar"]=>
  int(1)
  [0]=>
  int(2)
}
int(5)