How to implement an array sorting in php

In PHP, sorting is a frequently used operation, which can help us organize and display data according to different needs. Array sorting is one of the functions. This article will introduce how to use PHP to implement an array sorting.

1. Sorting function

PHP has many built-in array sorting functions. These functions are very practical in development. The following are some commonly used sorting functions:

1. sort (): Sort the array in ascending order
2. rsort(): Sort the array in descending order
3. asort(): Sort the array in ascending order and retain the original index relationship
4. arsort(): Sort the array in descending order and retain the original index relationship
5. ksort(): Sort the array in ascending order by key name
6. krsort(): Sort the array in descending order by key name Sorting
7. usort(): Customize sorting rules for sorting
8. uasort(): Customize sorting rules for sorting and retain the original index relationship
9. uksort(): Self Define sorting rules to sort by key name

2. Usage example

Let’s look at a simple example. Suppose we have an array that contains some numeric elements. We need Sort these numbers.

$arr ​​= array(3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5);
sort($arr);
print_r($arr);
?>

The output result is as follows:

Array
(

[0] => 1
[1] => 1
[2] => 2
[3] => 3
[4] => 3
[5] => 4
[6] => 5
[7] => 5
[8] => 5
[9] => 6
[10] => 9

)

This is a simple example of bubble sort. Bubble sort is a simple sorting algorithm and the easiest sorting algorithm for us to understand.

3. Custom sorting

If we need to customize the sorting rules, we can use the usort() and uasort() functions to achieve it. These functions work the same, the only difference is how they handle the indexing of the original array. Let's look at an example of custom sorting below.

$arr ​​= array(

array('name' => 'Tom', 'age' => 18),
array('name' => 'Jerry', 'age' => 16),
array('name' => 'Alice', 'age' => 19),
array('name' => 'Frank', 'age' => 25)</p>
<p>);</p>
<p>// Sort according to age field<br>function cmp($a, $ b)<br>{</p>
<pre class="brush:php;toolbar:false">if ($a['age'] > $b['age']) {
    return 1;
} elseif ($a['age'] < $b[&#39;age&#39;]) {
    return -1;
} else {
    return 0;
}

}

usort($arr, "cmp");
print_r($arr);
?>

The output results are as follows:

Array
(

[0] => Array
    (
        [name] => Jerry
        [age] => 16
    )

[1] => Array
    (
        [name] => Tom
        [age] => 18
    )

[2] => Array
    (
        [name] => Alice
        [age] => 19
    )

[3] => Array
    (
        [name] => Frank
        [age] => 25
    )

)

In the above code, we define a custom sorting function cmp(), which is based on the The age field of each element is compared. If the age value in the a element is greater than the age value in the b element, 1 is returned, that is, the a element should be ranked behind the b element; if the age value in the a element is less than the age value in the b element, The age value returns -1, that is, the a element should be ranked in front of the b element; if the age value in the a element is equal to the age value in the b element, 0 is returned, that is, the a element and the b element are the same, and no sorting is required. Finally, we use the usort() function to sort the array $arr according to custom rules, and use the print_r() function to output the result.

Summary

Through the introduction of this article, we have learned the basic knowledge and common functions of array sorting in PHP, and can choose the appropriate sorting function to sort the array according to actual needs. For complex sorting needs, we can use custom sorting functions. In actual development, it is very important to master the knowledge of array sorting.

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