Forgot to add more detail that...

I have tested files encoded in ASCII, UTF-8 w/ BOM and UTF-8 w/o BOM on both PHP4 and PHP5 (5.0.5)
Found no problem with ASCII and UTF-8 w/o BOM. Only UTF-8 w/ BOM has problem.
Also I found no problem with PHP 5.0.5. So that this problem should not caused by my INI file, I guess ;).

Thank you for this bug report. To properly diagnose the problem, we
need a short but complete example script to be able to reproduce
this bug ourselves. 

A proper reproducing script starts with <?php and ends with ?>,
is max. 10-20 lines long and does not require any external 
resources such as databases, etc.

If possible, make the script source available online and provide
an URL to it here. Try to avoid embedding huge scripts into the report.

Script to reproduce the bug
============================

<?

$dir = dirname(__FILE__) . '/';
$ascii = parse_ini_file($dir . 'test_ascii.ini', true);
$utf8bom = parse_ini_file($dir . 'test_utf8bom.ini', true);
$utf8 = parse_ini_file($dir . 'test_utf8.ini', true);
print_r($ascii);
print_r($utf8bom);
print_r($utf8);

?>

Unsatisfied Result
===================
(Don't worry about the value, just check the difference of array structure)

Array
(
    [Section1] => Array
        (
            [Aval] => &#3607;&#3604;&#3626;&#3629;&#3610; &#3607;&#3604;&#3626;&#3629;&#3610; (Test Test)
            [Bval] => &#3652;&#3607;&#3618;
        )

    [Section2] => Array
        (
            [Cval] => Bar
            [Dval] => Foo
        )

)
Array
(
    [Aval] => &#3648;&#3608;?&#3648;&#3608;?&#3648;&#3608;&#3594;&#3648;&#3608;&#3597;&#3648;&#3608;&#65533; &#3648;&#3608;?&#3648;&#3608;?&#3648;&#3608;&#3594;&#3648;&#3608;&#3597;&#3648;&#3608;&#65533; (Test Test)
    [Bval] => &#3648;&#3609;&#65533;&#3648;&#3608;?&#3648;&#3608;&#3586;
    [Section2] => Array
        (
            [Cval] => Bar
            [Dval] => Foo
        )

)
Array
(
    [Section1] => Array
        (
            [Aval] => &#3648;&#3608;?&#3648;&#3608;?&#3648;&#3608;&#3594;&#3648;&#3608;&#3597;&#3648;&#3608;&#65533; &#3648;&#3608;?&#3648;&#3608;?&#3648;&#3608;&#3594;&#3648;&#3608;&#3597;&#3648;&#3608;&#65533; (Test Test)
            [Bval] => &#3648;&#3609;&#65533;&#3648;&#3608;?&#3648;&#3608;&#3586;
        )

    [Section2] => Array
        (
            [Cval] => Bar
            [Dval] => Foo
        )

)

Try testing a demo at http://www.theguru.co.th/zybersup/test_parse_ini.php
(May not keep there more than 2 months)

Please provide access to the exact .ini file that is problematic. I could not reproduce this on PHP 4 or 5.

You can get the testing INI files from the same place of the testing script.

http://theguru.co.th/zybersup/test_utf8.ini
http://theguru.co.th/zybersup/test_utf8bom.ini
http://theguru.co.th/zybersup/test_utf8ascii.ini

Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

The reason this happens is because BOM is immediately adjacent to the "[Section 1]" portion. PHP 4 does not support Unicode. Thus, the parser cannot parse that line properly and treats the entries in that section as being global. You can either fix this by putting a newline before [Section 1] or upgrading to PHP 6.