How to reverse and reverse order a PHP array

How to reverse and reverse a PHP array

In PHP, an array is a commonly used data structure that can store and manipulate large amounts of data. Sometimes we need to reverse or reverse the array to meet specific needs. This article will introduce how to use PHP to reverse and reverse an array, and give corresponding code examples.

1. Reverse an array

Reversing an array means rearranging the elements in the array in reverse order according to their original order. PHP provides a variety of methods to reverse arrays. Two commonly used methods are introduced below.

1. Using the array_reverse() function

The array_reverse() function is a built-in function in PHP that is used to reverse the order of elements in an array. It can accept an array as a parameter and return a new array with the elements in the reverse order of the original array.

Code example:

$original_array = array("apple", "banana", "cherry");
$reversed_array = array_reverse($original_array);

print_r($reversed_array);

Output result:

Array
(
    [0] => cherry
    [1] => banana
    [2] => apple
)

2. Use foreach loop to output in reverse order

In addition to using the array_reverse() function , you can also use a foreach loop to output the elements in the array in reverse order. This method directly modifies the array itself without creating a new array.

Code example:

$original_array = array("apple", "banana", "cherry");
$reversed_array = [];

foreach ($original_array as $value) {
    array_unshift($reversed_array, $value);
}

print_r($reversed_array);

Output result:

Array
(
    [0] => cherry
    [1] => banana
    [2] => apple
)

2. Reverse array

Reverse array means to arrange the elements in the array from large to large according to the index. Arrange them in small order. PHP also provides a variety of methods to perform reverse order operations on arrays. Two commonly used methods are introduced below.

1. Use the rsort() function

The rsort() function is a built-in function in PHP that is used to sort arrays in reverse order. It can accept an array as a parameter and directly modify the order of elements of the array itself.

Code example:

$original_array = array("apple", "banana", "cherry");
rsort($original_array);

print_r($original_array);

Output result:

Array
(
    [0] => cherry
    [1] => banana
    [2] => apple
)

2. Use foreach loop to output in reverse order

It is similar to reversing the array, in reverse order Output arrays can also be implemented using a foreach loop. Just use reverse indexing to get elements when traversing the array.

Code example:

$original_array = array("apple", "banana", "cherry");
$reverse_array = [];

for ($i = count($original_array) - 1; $i >= 0; $i--) {
    $reverse_arr[] = $original_array[$i];
}

print_r($reverse_array);

Output result:

Array
(
    [0] => cherry
    [1] => banana
    [2] => apple
)

Summary:

Through the above code example, we can see that PHP provides a variety of methods to Reversing and reversing arrays. Choosing the appropriate method based on actual needs can improve the efficiency and readability of the code. At the same time, mastering these methods is also an important skill for us to handle array operations in daily development.

Reference:

• PHP Manual: array_reverse - https://www.php.net/manual/en/function.array-reverse.php
• PHP Manual: rsort - https://www.php.net/manual/en/function.rsort.php

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