Description:
------------
When running the test script with PHP 5.3.6 (and PHP 5.3.5) on Ubuntu 11.04 (64 bit) from command line, following message shown up.

PHP Notice:  Use of undefined constant self - assumed 'self' in /path_to_the_PHP_script on line 5
PHP Stack trace:
PHP   1. {main}() /path_to_the_PHP_script:0
PHP   2. TestArray::flatten() /path_to_the_PHP_script:25

The test script runs fine with PHP 5.3.5 on Ubuntu 11.04 (32 bit).

Test script:
---------------
<?php
class TestArray {
	public static function flatten(array $arr) {
		$data = array();
		array_walk_recursive($arr, array(self, 'appendToArray'), &$data);
		return $data;
	}

	protected static function appendToArray($val, $key, array &$arr) {
		$arr[] = $val;
	}
}

$arr = array(
	'a',
	array(
		'b',
		array(
			'c',
			'd',
		),
	),
);

print_r(TestArray::flatten($arr));
?>


Expected result:
----------------
Array
(
    [0] => a
    [1] => b
    [2] => c
    [3] => d
)


Actual result:
--------------
PHP Notice:  Use of undefined constant self - assumed 'self' in /path_to_the_PHP_script on line 5
PHP Stack trace:
PHP   1. {main}() /path_to_the_PHP_script:0
PHP   2. TestArray::flatten() /path_to_the_PHP_script:25
Array
(
    [0] => a
    [1] => b
    [2] => c
    [3] => d
)