(PHP 5 >= 5.2.0, PHP 7, PHP 8)
ArrayObject::uasort — Sort the entries with a user-defined comparison function and maintain key association
This function sorts the entries such that keys maintain their correlation with the entry that they are associated with, using a user-defined comparison function.
This is used mainly when sorting associative arrays where the actual element order is significant.
注意:
如果两个成员完全相同，那么它们将保持原来的顺序。 在 PHP 8.0.0 之前，它们在排序数组中的相对顺序是未定义的。
callback在第一个参数小于，等于或大于第二个参数时，该比较函数必须相应地返回一个小于，等于或大于 0 的整数。
总是返回 true。
示例 #1 ArrayObject::uasort() example
<?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' => -9, 'e' => 2, 'f' => 5, 'g' => 3, 'h' => -4);
$arrayObject = new ArrayObject($array);
print_r($arrayObject);
// Sort and print the resulting array
$arrayObject->uasort('cmp');
print_r($arrayObject);
?>以上示例会输出：
Array
(
[a] => 4
[b] => 8
[c] => -1
[d] => -9
[e] => 2
[f] => 5
[g] => 3
[h] => -4
)
Array
(
[d] => -9
[h] => -4
[c] => -1
[e] => 2
[g] => 3
[a] => 4
[f] => 5
[b] => 8
)