How to Sort Arrays in PHP 5

Sorting arrays is a fundamental operation in programming. In PHP, there are several built-in functions to sort arrays in various ways. This tutorial will cover different methods to sort arrays in PHP 5, including sorting by values, keys, and custom sorting. We will also discuss how to sort arrays in ascending and descending order.

Types of Array Sorting Functions in PHP

• sort(): Sorts an indexed array in ascending order.
• rsort(): Sorts an indexed array in descending order.
• asort(): Sorts an associative array in ascending order, according to the value.
• arsort(): Sorts an associative array in descending order, according to the value.
• ksort(): Sorts an associative array in ascending order, according to the key.
• krsort(): Sorts an associative array in descending order, according to the key.
• usort(): Sorts an array by values using a user-defined comparison function.

1. Sorting Indexed Arrays

Using sort()

The sort() function sorts an indexed array in ascending order:

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

Output:

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

Using rsort()

The rsort() function sorts an indexed array in descending order:

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

Output:

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

2. Sorting Associative Arrays

Using asort()

The asort() function sorts an associative array in ascending order, according to the value:

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

Output:

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

Using arsort()

The arsort() function sorts an associative array in descending order, according to the value:

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

Output:

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

Using ksort()

The ksort() function sorts an associative array in ascending order, according to the key:

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

Output:

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

Using krsort()

The krsort() function sorts an associative array in descending order, according to the key:

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

Output:

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

3. Custom Sorting with usort()

The usort() function allows you to sort an array using a user-defined comparison function. Here’s an example:

<?php
$array = array(4, 2, 8, 6);

function compare($a, $b) {
    return $a - $b; // Ascending order
}

usort($array, 'compare');
print_r($array);
?>

Output:

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

Conclusion

Sorting arrays in PHP is a straightforward process thanks to the variety of built-in functions available. Whether you are working with indexed or associative arrays, PHP provides you with flexible options to sort your data as needed. Understanding these functions will help you efficiently manage and display your data.

Feel free to explore these functions further and experiment with custom sorting based on your specific requirements!