保持数组在PHP中排序

$array = array("apple", "orange", "banana", "grape");
asort($array);

foreach ($array as $key => $value) {
    echo $key . ": " . $value . "<br>";
}

0: apple
1: banana
2: grape
3: orange

$array = array("apple", "orange", "banana", "grape");
ksort($array);

foreach ($array as $key => $value) {
    echo $key . ": " . $value . "<br>";
}

0: apple
1: orange
2: banana
3: grape

$array = array("apple", "orange", "banana", "grape");
arsort($array);

foreach ($array as $key => $value) {
    echo $key . ": " . $value . "<br>";
}

3: orange
2: banana
1: grape
0: apple

$array = array("apple", "orange", "banana", "grape");

function cmp($a, $b) {
    if ($a == $b) {
        return 0;
    }
    return ($a < $b) ? -1 : 1;
}

usort($array, "cmp");

foreach ($array as $key => $value) {
    echo $key . ": " . $value . "<br>";
}

0: apple
1: banana
2: grape
3: orange