note 97932 deleted from function.uasort by degeberg
| From: | degeberg@php.net | Date: | Sun, 16 May 2010 21:16:39 +0000 |
| Subject: | note 97932 deleted from function.uasort by degeberg | ||
| References: | 1 | Groups: | php.notes |
| Request: | Send a blank email to php-notes+get-169311@lists.php.net to get a copy of this message | ||
Note Submitter: dave+php at davereid dot net
----
Note that your sort function should *never* return a value of 0 because it will still cause two
items of 'equal' value to be swapped.
Using the cmp() function in the documentation with two keys that have the same values:
<?php
// Comparison function
function cmp($a, $b) {
if ($a == $b) {
return 0;
}
return ($a < $b) ? -1 : 1;
}
// Array to be sorted
$array = array('a' => 4, 'b' => 8, 'c' => -1, 'd'
=> -1);
print_r($array);
// Sort and print the resulting array
uasort($array, 'cmp');
print_r($array);
?>
Results in the elements with keys 'c' and 'd' being swapped around:
<?php
Array
(
[a] => 4
[b] => 8
[c] => -1
[d] => -1
)
Array
(
[d] => -1
[c] => -1
[a] => 4
[b] => 8
)
?>
If you remove the return '0' condition in cmp(), you get what everyone would expect, that
'c' and 'd' have not been swapped.
<?php
Array
(
[a] => 4
[b] => 8
[c] => -1
[d] => -1
)
Array
(
[c] => -1
[d] => -1
[a] => 4
[b] => 8
)
?>