Detailed explanation of examples of random shuffling and reverse ordering of PHP arrays

Random shuffling and reverse order of PHP arrays

In the first two articles "How to sort PHP arrays" and " PHP Array Reverse Order" introduces two sets of functions, one in ascending order and one in reverse order (descending order). Today, in this article, we will introduce to you the random order and reverse order of arrays!

1. What is random disorder? (shuffle)

#shuffle is to disrupt the array.

Use the shuffle function to randomly sort the elements in the array.

The shuffle syntax structure is as follows:

bool shuffle ( array &$array )

Parameters	Description
array	Required. Specifies the array to adapt to.

This function scrambles (randomly arranges the order of cells) an array. It uses a pseudo-random number generator and is not suitable for cryptography situations.

shuffle instance usage:

Let’s take an example to explain the shuffle function in detail. The specific code is as follows:

<?php
header("Content-Type:text/html; charset=utf-8");
$arr=array("name" => "PHP中文网", "url" => "www.php.cn", "tom" => "100","hank" => "60");
shuffle($arr); // 将数组的值随机排序
print_r($arr);
?>

The output result is:

The above example will output different results every time you refresh the browser. I won’t take more screenshots here. You can try it locally!

Note: After the associative array is shuffled, the keys will be lost, as you should be able to see from the above example!

2. What is reverse order? (array_reverse)

array_reverse — Returns an array with the reverse order of the cells. Reverse order is to reverse the order of each element in an original array,

The syntax format of array_reverse is as follows:

array array_reverse ( array $array [, bool $preserve_keys = false ] )

array_reverse() accepts array array as input and returns a new array with the cells in reverse order. If preserve_keys is TRUE, the original key names are retained.

Instructions:

1. Reverse order ≠ Descending order

2. If The array is an associative array

When the key is a character, the reverse order will not be affected, the key will still be retained

When the key is a number, after the reverse order The default keys will be reset to 0, 1, 2...

When the second parameter is true, the keys are numbers, and the numeric keys are retained in reverse order

Let’s look at the example code of when the key is a number:

<?php
header("Content-Type:text/html; charset=utf-8");
$arr=array("100" => "PHP中文网", "200" => "www.php.cn", "300" => "百度","400" => "搜狗");
$array = array_reverse($arr);//数组反序，将数组的元素反转
print_r($arr);
echo "<br>";
print_r($array);
?>

The output result is:

The key is Keep the key value when numbersSample code:

<?php
header("Content-Type:text/html; charset=utf-8");
$arr=array("100" => "PHP中文网", "200" => "www.php.cn", "300" => "百度","400" => "搜狗");
$array = array_reverse($arr,true);//数组反序，将数组的元素反转
print_r($arr);
echo "<br>";
print_r($array);
?>

The output result is:

As can be seen from the above code, the key is When numbers are used, the key value is retained, which means the second parameter of array_reverse is true!

The key is when the key is a characterSample code:

<?php
header("Content-Type:text/html; charset=utf-8");
$arr=array("name" => "PHP中文网", "ID" => "www.php.cn", "name1" => "百度","name2" => "搜狗");
$array = array_reverse($arr);//数组反序，将数组的元素反转
print_r($arr);
echo "<br>";
print_r($array);
?>

The output result is:

array_reverse function When the array is reversed, if the key value is a string, the key value will be retained!

Note: When using the array_reverse function, the original array will not be affected, and a new array will be returned!

In this article we introduce the reverse order and disorder of the array. In the next article, we will introduce the equal division, replacement and interception of arrays. For detailed introduction, please read "Interception, equal division and replacement of partial arrays of PHP arrays"!

【Related tutorial recommendations】

1. Related topic recommendations: "php array (Array)"

2. Related video course recommendations: "Other array functions: array_rand()/array_sum()/shuffle()/range()》

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