How to sort an array of UTF-8 strings?

$a = array( 'Кръстев', 'Делян1', 'делян1', 'Делян2', 'делян3', 'кръстев' );$col = new \Collator('bg_BG');$col->asort( $a );var_dump( $a );

Prints:

array  2 => string 'делян1' (length=11)  1 => string 'Делян1' (length=11)  3 => string 'Делян2' (length=11)  4 => string 'делян3' (length=11)  5 => string 'кръстев' (length=14)  0 => string 'Кръстев' (length=14)

The Collator class is defined in PECL intl extension. It is distributed with PHP 5.3 sources but might be disabled for some builds. E.g. in Debian it is in package php5-intl .

Collator::compare is useful for usort.

Update on this issue:

Even though the discussion around this problem revealed that we could have discovered a PHP bug with strcoll() and/or setlocale(), this is clearly not the case. The problem is rather a limitation of the Windows CRT implementation of setlocale() (PHPs setlocale() is just a thin wrapper around the CRT call). The following is a citation of the MSDN page "setlocale, _wsetlocale":

The set of available languages, country/region codes, and code pages includes all those supported by the Win32 NLS API except code pages that require more than two bytes per character, such as UTF-7 and UTF-8. If you provide a code page like UTF-7 or UTF-8, setlocale will fail, returning NULL. The set of language and country/region codes supported by setlocale is listed in Language and Country/Region Strings.

It therefore is impossible to use locale-aware string operations within PHP on Windows when strings are multi-byte encoded.

Eventually this problem cannot be solved in a simple way without using recoded strings (UTF-8 → Windows-1252 or ISO-8859-1) as suggested by ΤΖΩΤΖΙΟΥ due to an obvious PHP bug as discovered by Huppie.To summarize the problem, I created the following code snippet which clearly demonstrates that the problem is the strcoll() function when using the 65001 Windows-UTF-8-codepage.

function traceStrColl($a, $b) {    $outValue=strcoll($a, $b);    echo "$a $b $outValue\r\n";    return $outValue;}$locale=(defined('PHP_OS') && stristr(PHP_OS, 'win')) ? 'German_Germany.65001' : 'de_DE.utf8';$string="ABCDEFGHIJKLMNOPQRSTUVWXYZÄÖÜabcdefghijklmnopqrstuvwxyzäöüß";$array=array();for ($i=0; $i<mb_strlen($string, 'UTF-8'); $i++) {    $array[]=mb_substr($string, $i, 1, 'UTF-8');}$oldLocale=setlocale(LC_COLLATE, "0");var_dump(setlocale(LC_COLLATE, $locale));usort($array, 'traceStrColl');setlocale(LC_COLLATE, $oldLocale);var_dump($array);

The result is:

string(20) "German_Germany.65001"a B 2147483647[...]array(59) {  [0]=>  string(1) "c"  [1]=>  string(1) "B"  [2]=>  string(1) "s"  [3]=>  string(1) "C"  [4]=>  string(1) "k"  [5]=>  string(1) "D"  [6]=>  string(2) "ä"  [7]=>  string(1) "E"  [8]=>  string(1) "g"  [...]

The same snippet works on a Linux machine without any problems producing the following output:

string(10) "de_DE.utf8"a B -1[...]array(59) {  [0]=>  string(1) "a"  [1]=>  string(1) "A"  [2]=>  string(2) "ä"  [3]=>  string(2) "Ä"  [4]=>  string(1) "b"  [5]=>  string(1) "B"  [6]=>  string(1) "c"  [7]=>  string(1) "C"  [...]

The snippet also works when using Windows-1252 (ISO-8859-1) encoded strings (of course the mb_* encodings and the locale must be changed then).

I filed a bug report on bugs.php.net: Bug #46165 strcoll() does not work with UTF-8 strings on Windows. If you experience the same problem, you can give your feedback to the PHP team on the bug-report page (two other, probably related, bugs have been classified as bogus - I don't think that this bug is bogus ;-).

Thanks to all of you.