How to sort elements in php array

PHP array is a very commonly used data structure that can store a series of data values. In actual use, it will involve sorting the data. This article will introduce how to sort the elements of the PHP array.

1. The basic concept of array sorting

Array sorting refers to the process of arranging the elements in an array in a certain order. The purpose is to facilitate the search, storage, output, etc. of data. operate.

There are two functions for sorting arrays in PHP, namely sort() and rsort(). The sort() function is for ascending sorting and the rsort() function is for descending sorting.

2. Sort() function

The sort() function can sort the indexes of the PHP array from small to large. The syntax format of the sort() function is as follows:

sort($array);

where $array is the array that needs to be sorted.

The following is an example of sorting an array in ascending order:

<?php $fruits = array("apple", "orange", "grape", "banana");
sort($fruits);
print_r($fruits);
?>

The output results are as follows:

Array
(
    [0] => apple
    [1] => banana
    [2] => grape
    [3] => orange
)

It can be seen from the output results that the sort() function sorts the elements in the array The elements are arranged in alphabetical order, realizing the function of ascending order.

3. rsort() function

The rsort() function is similar to the sort() function, except that it sorts the elements of the array from large to small. The syntax format of the rsort() function is as follows:

rsort($array);

where $array is the array that needs to be sorted.

The following is an example of sorting an array in descending order:

<?php $numbers = array(4, 2, 8, 6);
rsort($numbers);
print_r($numbers);
?>

The output results are as follows:

Array
(
    [0] => 8
    [1] => 6
    [2] => 4
    [3] => 2
)

As can be seen from the output results, the rsort() function sorts the The elements are arranged in order from largest to smallest.

4. asort() function

asort() function can sort PHP arrays according to values. After sorting, the relationship between keys and values ​​remains unchanged. The syntax format of the function As follows:

asort($array);

Among them, $array is the array that needs to be sorted.

The following is an example of sorting an array in ascending order:

<?php $numbers = array(4, 2, 8, 6);
asort($numbers);
print_r($numbers);
?>

The output results are as follows:

Array
(
    [1] => 2
    [0] => 4
    [3] => 6
    [2] => 8
)

As can be seen from the output results, the asort() function sorts the elements in the array The elements are arranged in ascending order, while keeping the key-value association unchanged.

5. arsort() function

The arsort() function is similar to the asort() function, except that it sorts the elements of the array from large to small. The syntax format of the arsort() function is as follows:

arsort($array);

where $array is the array that needs to be sorted.

The following is an example of sorting an array in descending order:

<?php $numbers = array(4, 2, 8, 6);
arsort($numbers);
print_r($numbers);
?>

The output results are as follows:

Array
(
    [2] => 8
    [3] => 6
    [0] => 4
    [1] => 2
)

As can be seen from the output results, the arsort() function sorts the elements in the array The elements are arranged from largest to smallest, while keeping the key-value association unchanged.

6. ksort() function

The ksort() function can sort the PHP array according to the key, in order from small to large. The syntax format of the function is as follows:

ksort($array);

Among them, $array is the array that needs to be sorted.

The following is an example of sorting an array in ascending order:

<?php $numbers = array(
    "c" => 4,
    "a" => 2,
    "b" => 8,
    "d" => 6
);
ksort($numbers);
print_r($numbers);
?>

The output results are as follows:

Array
(
    [a] => 2
    [b] => 8
    [c] => 4
    [d] => 6
)

It can be seen from the output results that the ksort() function sorts the The elements are arranged in alphabetical order by key.

7. krsort() function

The krsort() function is similar to the ksort() function, except that it arranges the elements of the array in reverse order of keys. The syntax format of the function is as follows ：

krsort($array);

Among them, $array is the array that needs to be sorted.

The following is an example of sorting an array in descending order:

<?php $numbers = array(
    "c" => 4,
    "a" => 2,
    "b" => 8,
    "d" => 6
);
krsort($numbers);
print_r($numbers);
?>

The output results are as follows:

Array
(
    [d] => 6
    [c] => 4
    [b] => 8
    [a] => 2
)

It can be seen from the output results that the krsort() function sorts the elements in the array The elements are sorted in reverse order of keys.

Summary:

In PHP, sorting is a very common and important operation. You can quickly sort arrays using PHP's built-in functions. Of course, we can also use custom functions to sort array elements, which requires a deep understanding of PHP's array operations.

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