array_reverse — 返回单元顺序相反的数组
$array, bool $preserve_keys = false): array参数:
array
preserve_keys
true 会保留数字的键。 非数字的键则不受这个设置的影响，总是会被保留。1、示例
<?php
$input = array("php", 4.0, array("green", "red"));
$reversed = array_reverse($input);
print_r($input);
print_r($reversed);
?>
返回：返回了逆序数组，并对元素’php‘的key进行了的重新索引
Array
(
[0] => php
[1] => 4
[2] => Array
(
[0] => green
[1] => red
)
)
Array
(
[0] => Array
(
[0] => green
[1] => red
)
[1] => 4
[2] => php
)
2、保留原key，设置preserve_keys为true
<?php
$input = array("php", 4.0, array("green", "red"));
$preserved = array_reverse($input, true);
print_r($input);
print_r($preserved);
?>
返回:
Array
(
[0] => php
[1] => 4
[2] => Array
(
[0] => green
[1] => red
)
)
Array
(
[2] => Array
(
[0] => green
[1] => red
)
[1] => 4
[0] => php
)
原文：https://www.cnblogs.com/ttaylor/p/15096546.html