Where did you get the idea that that should work in the first place?
The correct way:

foo="{$FOO}barian"

Hello Jani,

Before I've submited this bug, I've tested this feature in php-5.2.5
where line foo=FOO"barian" returns [foo] => barbarian
so it works gracefully, in php5.3-dev it doesn't.

In my example FOO is a constant defined before parse_ini_file function.
In your example $FOO is undefined global variable isn't it?
Anyway changing ini file using your way doesn't work as expected, even
if there's no $FOO definition I should be expecting that
foo="{$FOO}barian"  returns [foo] => barian                          
                        not [foo] => FOO}barian

modified Test.ini using Jani's solution
-------------------------------------
[Topic]
number=1
string="test"
foo="{$FOO}barian"

PHP code:
--------
<?
define("FOO","bar");
print_r(parse_ini_file("test.ini",true));
?>

Expected result:
----------------
Array
(
    [Topic] => Array
        (
            [number] => 1
            [string] => test
            [foo] => barbarian
        )

)
Actual Result:
--------------
Array
(
    [Topic] => Array
        (
            [number] => 1
            [string] => test
            [foo] => FOO}barian
        )

)

I Hope it helps.
Best regards
Petr

Ah, now I see. I didn't have any machine to test with during the weekend so I got it wrong way. :D

In 5.3 the ini parsing has been improved, and along the line I broke some old stuff which I actually didn't think anyone relied upon.

I have to investigate and check if it's possible even to keep this old (and bad) syntax. Is it even documented anywhere?

I've used this syntax in 5.x versions till now.
I got most suggestions and ideas from official documentation and comment discussion http://php.net/manual/en/function.parse-ini-file.php
Maybe it's good idea to post there the new syntax usage change for versions >= 5.3
before it's officially changed in documentation on php5.3 stable release.

Regards
Petr

Hold your horses, I have a fix already, just waiting for commit..

And btw. Comments in the manual are not documented behaviour. :)

This bug has been fixed in CVS.

Snapshots of the sources are packaged every three hours; this change
will be in the next snapshot. You can grab the snapshot at
http://snaps.php.net/.
 
Thank you for the report, and for helping us make PHP better.