Correct way to reverse array in PHP

There are three ways to reverse an array in PHP: use the array_reverse() function to return a new array. Use a for loop to reverse manually, iterating over the array starting from the end. Use the rsort() and ksort() built-in functions to sort the array in descending order, then sort the keys, and perform indirect reversal.

The correct way to reverse an array in PHP

Reverse an array, that is, change the order of the elements in the array so that it is the same as the original The order is reversed. There are several ways to reverse an array in PHP.

1. array_reverse() function

The easiest way is to use the array_reverse() function. It returns a new array without modifying the original array:

$arr = [1, 2, 3, 4, 5];
$reversed = array_reverse($arr);

print_r($reversed); // 输出： [5, 4, 3, 2, 1]

2. for loop

If you don’t need to return a new array, you can use a for loop to reverse it manually Convert array:

$arr = [1, 2, 3, 4, 5];
$reversed = [];

// 从末尾开始遍历数组
for ($i = count($arr) - 1; $i >= 0; $i--) {
    $reversed[] = $arr[$i];
}

$arr = $reversed; // 替换原始数组

print_r($arr); // 输出： [5, 4, 3, 2, 1]

3. Built-in functions

PHP also provides other useful built-in functions, such as rsort() and ksort(), they can sort arrays in descending order. This can be used to reverse an array indirectly:

$arr = [1, 2, 3, 4, 5];

rsort($arr); // 降序排序
ksort($arr); // 按键排序

print_r($arr); // 输出： [5, 4, 3, 2, 1]

Practical Example

Suppose you have an array containing a list of order IDs, and you want to sort them from newest to oldest Orders are sorted sequentially. You can use the array_reverse() function:

$order_ids = [100, 101, 102, 103, 104];

$reversed_order_ids = array_reverse($order_ids);

// 按最新到最旧的顺序获取订单
foreach ($reversed_order_ids as $order_id) {
    // 处理订单
}

With these methods you can easily reverse a PHP array according to your needs.

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