How to reverse an array in php

In PHP, array_reverse() or array_flip() function can be used to achieve array reversal. array_reverse() can reverse the array elements. It will reverse the order of the elements in the original array, create a new array and return it. The syntax is "array_reverse(array,preserve)". array_flip() can reverse the array key-value pairs and exchange the positions of keys and values ​​in the array. The syntax is "array_flip(array)".

The operating environment of this tutorial: windows7 system, PHP8 version, DELL G3 computer

Array inversion can be divided into:

• Reverse the position of array elements

• Reverse the position of keys and values

In php, array_reverse is available () or array_flip() function to achieve.

Method 1: Use array_reverse() to reverse the position of array elements

array_reverse() function returns an array in the reverse order of elements; It flips the order of elements in the original array, creates a new array and returns it.

Grammar format:

array_reverse(array,preserve)

Parameters	Description
array	Required. Specifies an array.
preserve	Optional. Specifies whether to retain the original array key names. If set to TRUE, numeric keys will be preserved. Non-numeric keys are not affected by this setting and will always be retained. Possible values: true false

##Example:

<?php
header("Content-type:text/html;charset=utf-8");
$array= array("香蕉","苹果","梨子","橙子","橘子","榴莲");

var_dump(array_reverse($array));
var_dump(array_reverse($array,true));
?>

• The preserve parameter can be omitted and is used to specify whether to retain the key names of the original array (only for numeric key names, non-numeric keys are not affected).

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);
$arr =array("a"=>"Volvo","b"=>"BMW","c"=>"Toyota");
echo "原数组顺序：";
var_dump($arr);
echo "<br>数组反转后的顺序：";
var_dump(array_reverse($arr));
var_dump(array_reverse($arr,true));
?>

Method 2: Use array_flip() to reverse the positions of keys and values

array_flip() function can exchange the keys and values ​​in the array

<?php
header("Content-type:text/html;charset=utf-8");
$arr1=array("aaa"=>11,"bbb"=>22,"ccc"=>33);
echo "原数组：";
var_dump($arr1);

$arr2=array_flip($arr1);
echo "反转数组键值对的数组：";
var_dump($arr2);
?>

Recommended learning: "

PHP Video Tutorial"

The above is the detailed content of How to reverse an array in php. For more information, please follow other related articles on the PHP Chinese website!