I suppose you mean on windows right? As for any other OSes, you can install whatever the distribution provides, or manually compile the version you wish.

@a can you look to update to 5.1 for 5.5+? For what I see we have 5.0.

Good to know on other OSes. Will test it and check that it vorks...

Please try using this snapshot:

  http://snaps.php.net/php5.5-latest.tar.gz
 
For Windows:

  http://windows.php.net/snapshots/

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Looks like there may a bug in the PHP Intl code, after I downloaded and tested the latest PHP / PHP Intl (PECL). Got a Java version of it to work fine (based on icu4j). Someone else (cataphract) was able to get a C++ version working. Here's my script:
<?php
if (!extension_loaded('intl'))
   die('skip intl extension not enabled');
ini_set("intl.error_level", E_WARNING);
ini_set("intl.default_locale", "lo_LA");
echo INTL_ICU_VERSION;
$bi = IntlBreakIterator::createWordInstance('lo');
$myText =
"ພຣະທັມເຮັບເລີຄາດຄະເນລ່ວງໜ້າວ່າຄົນຈະຮູ້ແລະເຂົ້າໃຈເຖິງວຽກງານຂອງປະໂລຫິດໃນສະໄໝຂອງຊົນຊາດອິດສະລາເອນເພື່ອວ່າຜູ້ທີ່ຮັບຈົດໝາຍທີ່ຖືກບັນທຶກໄວ້ໃນພຣະທັມນີ້ຈະສາມາດເຂົ້າໃຈວ່າພຣະເຢຊູຊົງເຮັດສິ່ງໃດສຳລັບພວກເຂົາໃນສະຫວັນ";
$bi->setText($myText);
var_dump($bi->first());
var_dump($bi->next());
var_dump($bi->next());
var_dump($bi->next());
var_dump($bi->next());
var_dump($bi->next());
var_dump($bi->next());
?>

PHP Output:
52.1
int 0
int 597
int -1
int -1
int -1
int -1
int -1

The windows ICU version was upgraded to 51.2, you can get it from the snap http://windows.php.net/downloads/snaps/php-5.5/ (take one of the latest). As you use the PECL version, could you please decouple your report into a separate ticket and assign it to the PECL intl ext. As this ticket was about upgrading the ICU for the windows builds and it's done. Please give then which exact PHP version, platform, etc you've used to reproduce the wrong behavior, and what's the correct result you expect. With the intl ext in the core results might differ.

Thanks

Done. New bug submitted #66002 for PECL intl. Will test the Windows Snapshot on my Windows XP tomorrow. Thanks so much for your help!