PHP array_reverse

Summary: in this tutorial, you will learn how to use the PHP array_reverse() function to reverse the order of elements in an array.

Introduction to the PHP array_reverse() function

The array_reverse() function accepts an array and returns a new array with the order of elements in the input array reversed.

The following shows the array_reverse() function:

array_reverse ( array $array , bool $preserve_keys = false ) : array
Code language: PHP (php)

The array_reverse() function has two parameters:

  • $array is the input array
  • $preserve_keys determines if the numeric keys should be preserved. If $preserve_keys is true, the numeric key of elements in the new array will be preserved. The $preserve_keys doesn’t affect the non-numeric keys.

The array_reverse() doesn’t change the input array. Instead, it returns a new array.

PHP array_reverse() function examples

Let’s take some example of using the PHP array_reverse() function.

1) Simple PHP array_reverse() function example

The following example uses the array_reverse() function to reverse the order of an array:

<?php $numbers = [10, 20, 30]; $reversed = array_reverse($numbers); print_r($reversed); print_r($numbers);
Code language: HTML, XML (xml)

Output:

Array ( [0] => 30 [1] => 20 [2] => 10 ) Array ( [0] => 10 [1] => 20 [2] => 30 )
Code language: plaintext (plaintext)

How it works.

  • First, define an array of three numbers 10, 20, 30.
  • Then, use the array_reverse() function to create a new array with the order of elements in the $numbers array reversed.
  • Finally, show the reversed array and the $numbers array. As you can see, the $numbers array doesn’t change.

2) Using the PHP array_reverse() function to preserve numeric keys

The following example uses the array_reverse() function to reverse elements of an array. However, it preserves the keys of the elements:

<?php $book = [ 'PHP Awesome', 999, ['Programming', 'Web development'], ]; $preserved = array_reverse($book, true); print_r($preserved);
Code language: HTML, XML (xml)

Output:

Array ( [2] => Array ( [0] => Programming [1] => Web development ) [1] => 999 [0] => PHP Awesome )
Code language: PHP (php)

Summary

  • Use the PHP array_reverse() function to reverse the order of elements in an array.
  • Set the $preserve_keys to true to preserve the keys in the original array.
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