Description:
------------
When running the small examples below, the first version works fine, while the second triggers a warning:
Warning: array_map() expects parameter 1 to be a valid callback, cannot access private method Bar::callBack() in /tmp/private_callback-buggy.php on line 6

The only difference between the two code snippets is the callback being camel case in the second example. Both versions work fine with 5.2.

Reproduce code:
---------------
First example:

<?php
class Foo
{
    public function __construct(array $data)
    {
		var_dump(array_map(array($this, 'callback'), $data));
    }
    
    private function callback($value)
    {
        if (!is_array($value)) {
            return stripslashes($value);
        }
		return array_map(array($this, 'callback'), $value);
    }
}


class Bar extends Foo
{
}

var_dump(new Bar(array('foo' => 'bar', 'baz' => array('one', 'two\"'))));


Second example:

<?php
class Foo
{
    public function __construct(array $data)
    {
		var_dump(array_map(array($this, 'callBack'), $data));
    }
    
    private function callBack($value)
    {
        if (!is_array($value)) {
            return stripslashes($value);
        }
		return array_map(array($this, 'callBack'), $value);
    }
}


class Bar extends Foo
{
}

var_dump(new Bar(array('foo' => 'bar', 'baz' => array('one', 'two\"'))));