Question

Is there any example of using SORT_LOCALE_STRING where it would give a different result to the default SORT_STRING when using array_unique?

Here is some code that shows how you can get different results between SORT_STRING, SORT_REGULAR, SORT_NUMERIC.

<?php
$list = array(
  '0',
  null,
  0,
  10,
  '10.0',
  '1e1',
  false,
  ''
);
var_dump(array_unique($list));
var_dump(array_unique($list, SORT_NUMERIC));
var_dump(array_unique($list, SORT_REGULAR));

Output:

array(5) {
  [0]=>
  string(1) "0"
  [1]=>
  NULL
  [3]=>
  int(10)
  [4]=>
  string(4) "10.0"
  [5]=>
  string(3) "1e1"
}
array(2) {
  [0]=>
  string(1) "0"
  [3]=>
  int(10)
}
array(4) {
  [0]=>
  string(1) "0"
  [1]=>
  NULL
  [3]=>
  int(10)
  [7]=>
  string(0) ""
}

Please help me find an example that shows a use for SORT_LOCALE_STRING.

Answer 1

I guess in german, ß and ss are considered lexicographically equal I think. Basically, they should be considered the same character and sort as such. If you don’t use a locale sensitive string comparison(sorting is string comparison), then, I think it’s pretty obvious those two strings wont compare as being equal.

$array = array('ß', 't', 'ss');
//binary safe transport of the above chars as present in my text editor
$array = unserialize(base64_decode('YTozOntpOjA7czoxOiLfIjtpOjE7czoxOiJ0IjtpOjI7czoyOiJzcyI7fQ=='));
setlocale(LC_ALL, 'de_DE@euro', 'de_DE', 'deu_deu');
echo setlocale(LC_ALL, '0'), "\n";
var_dump(strcoll('ß', 'ss'));
var_dump(array_unique($array, SORT_LOCALE_STRING));

yields, on my machine(win7, php5.4rc2)

German_Germany.1252
int(0)
array(2) {
  [0]=>
  string(1) "ß"
  [1]=>
  string(1) "t"
}