How to Sort Array in PHP: Syntax and Examples

In PHP, you can sort arrays using built-in functions like sort() for ascending order and rsort() for descending order. For associative arrays, use asort() to sort by values or ksort() to sort by keys.

Syntax

PHP provides several functions to sort arrays depending on your needs:

• sort(array): Sorts array values in ascending order and reindexes keys.
• rsort(array): Sorts array values in descending order and reindexes keys.
• asort(array): Sorts associative array by values, preserving keys.
• ksort(array): Sorts associative array by keys in ascending order.

php

bool sort(array &$array)
bool rsort(array &$array)
bool asort(array &$array)
bool ksort(array &$array)

Example

This example shows how to sort a simple array in ascending and descending order, and how to sort an associative array by values and keys.

php

<?php
// Simple array
$numbers = [4, 2, 8, 6];
sort($numbers); // Ascending
print_r($numbers);

rsort($numbers); // Descending
print_r($numbers);

// Associative array
$fruits = ["d" => "lemon", "a" => "orange", "b" => "banana", "c" => "apple"];
asort($fruits); // Sort by values
print_r($fruits);

ksort($fruits); // Sort by keys
print_r($fruits);
?>

Output

Array
(
    [0] => 2
    [1] => 4
    [2] => 6
    [3] => 8
)
Array
(
    [0] => 8
    [1] => 6
    [2] => 4
    [3] => 2
)
Array
(
    [c] => apple
    [b] => banana
    [a] => orange
    [d] => lemon
)
Array
(
    [a] => orange
    [b] => banana
    [c] => apple
    [d] => lemon
)

Common Pitfalls

One common mistake is using sort() on associative arrays expecting keys to be preserved; sort() reindexes keys which can cause data loss of keys. Also, sorting functions modify the original array instead of returning a new sorted array, so you must pass the array by reference or use the array after sorting.

Wrong way:

$arr = ["a" => 3, "b" => 1];
sort($arr);
// Keys lost after sort()

Right way:

$arr = ["a" => 3, "b" => 1];
asort($arr); // preserves keys

php

$arr = ["a" => 3, "b" => 1];
sort($arr);
print_r($arr);

$arr = ["a" => 3, "b" => 1];
asort($arr);
print_r($arr);

Output

Array
(
    [0] => 1
    [1] => 3
)
Array
(
    [b] => 1
    [a] => 3
)

Quick Reference

Here is a quick summary of PHP array sorting functions:

Function	Description	Preserves Keys?
sort()	Sorts array values ascending, reindexes keys	No
rsort()	Sorts array values descending, reindexes keys	No
asort()	Sorts associative array by values ascending	Yes
arsort()	Sorts associative array by values descending	Yes
ksort()	Sorts associative array by keys ascending	Yes
krsort()	Sorts associative array by keys descending	Yes

Key Takeaways

Use sort() for simple arrays to sort values ascending and reindex keys.

Use asort() or ksort() to sort associative arrays while keeping keys intact.

Sorting functions modify the original array; they do not return a new sorted array.

rsort() and arsort() sort arrays in descending order.

Avoid using sort() on associative arrays if you want to keep keys.