How to make array flashback in php (3 methods)

In PHP programming, it is often necessary to sort arrays, including backward sorting of arrays. Although there are many ways to implement PHP array flashback, in this article, I will share the method to implement PHP array flashback using PHP built-in function array_reverse ().

1. Basic usage of array_reverse() function

PHP built-in function array_reverse() can help us reverse the order of the array. The following is its commonly used calling method:

array array_reverse ( array $array , bool $preserve_keys = FALSE )

Among them, the $array parameter is the array to be reversed. If the $preserve_keys parameter is set to true, the original key values ​​of the array will be retained. If set to false or not set, the array key values ​​will be reset.

Let’s look at a simple example:

$arr = array('a', 'b', 'c', 'd');
$reverse = array_reverse($arr);
print_r($reverse);

The output result is:

Array
(
    [0] => d
    [1] => c
    [2] => b
    [3] => a
)

As you can see, the array_reverse() function will change the order of the elements of the array to from Arrange in reverse order starting from the last element.

2. Use array_reverse() to implement multi-dimensional array reverse order

When we want to arrange a multi-dimensional array in reverse order, we need to process the subarray first. For multidimensional arrays, we can use array_map() to apply the array_reverse() function to each subarray, and then use the array_reverse() function to reverse the order of the entire array.

The following is a simple example of reverse order of a multi-dimensional array:

$arr = array(
    array('a', 'b', 'c'),
    array('d', 'e', 'f'),
    array('g', 'h', 'i')
);
$reverse = array_reverse(array_map('array_reverse', $arr));
print_r($reverse);

The output result is:

Array
(
    [0] => Array
        (
            [0] => i
            [1] => h
            [2] => g
        )

    [1] => Array
        (
            [0] => f
            [1] => e
            [2] => d
        )

    [2] => Array
        (
            [0] => c
            [1] => b
            [2] => a
        )

)

3. Use krsort() to implement the reverse order of an associative array

For associative arrays, we can use the krsort() function to implement reverse order. The krsort() function can sort associative arrays in reverse order by key name without changing their key values.

The following is a simple example of associative array reverse order:

$arr = array(
    "a" => "apple",
    "b" => "banana",
    "c" => "cat"
);
krsort($arr);
print_r($arr);

The output result is:

Array
(
    [c] => cat
    [b] => banana
    [a] => apple
)

As you can see, the krsort() function sorts the key names of the associative array in reverse order Arrange without changing their key values.

Summary

This article introduces how to use the built-in function array_reverse() to implement array reverse in PHP. We also give examples of applying this function to multidimensional arrays and associative arrays. Mastering these techniques can help you in your PHP development.

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