PHP Sorting Arrays

PHP Functions For Sorting Arrays

In the previous chapter, you've learned the essentials of PHP arrays i.e. what arrays are, how to create them, how to view their structure, how to access their elements etc. You can do even more things with arrays like sorting the elements in any order you like.

PHP comes with a number of built-in functions designed specifically for sorting array elements in different ways like alphabetically or numerically in ascending or descending order. Here we'll explore some of these functions most commonly used for sorting arrays.

• sort() and rsort() — For sorting indexed arrays
• asort() and arsort() — For sorting associative arrays by value
• ksort() and krsort() — For sorting associative arrays by key

Sorting Indexed Arrays in Ascending Order

The sort() the function is used for sorting the elements of the indexed array in ascending order (alphabetically for letters and numerically for numbers).

<?php
// Define array
$colors = array("Red", "Green", "Blue", "Yellow");
 
// Sorting and printing array
sort($colors);
print_r($colors);
?>

This print_r() statement gives the following output:

Array ( [0] => Blue [1] => Green [2] => Red [3] => Yellow )

Similarly you can sort the numeric elements of the array in ascending order.

<?php
// Define array
$numbers = array(1, 2, 2.5, 4, 7, 10);
 
// Sorting and printing array
sort($numbers);
print_r($numbers);
?>

This print_r() statement gives the following output:

Array ( [0] => 1 [1] => 2 [2] => 2.5 [3] => 4 [4] => 7 [5] => 10 )

---

Sorting Indexed Arrays in Descending Order

The rsort() function is used for sorting the elements of the indexed array in descending order (alphabetically for letters and numerically for numbers).

<?php
// Define array
$colors = array("Red", "Green", "Blue", "Yellow");
 
// Sorting and printing array
rsort($colors);
print_r($colors);
?>

This print_r() statement gives the following output:

Array ( [0] => Yellow [1] => Red [2] => Green [3] => Blue )

Similarly you can sort the numeric elements of the array in descending order.

<?php
// Define array
$numbers = array(1, 2, 2.5, 4, 7, 10);
 
// Sorting and printing array
rsort($numbers);
print_r($numbers);
?>

This print_r() statement gives the following output:

Array ( [0] => 10 [1] => 7 [2] => 4 [3] => 2.5 [4] => 2 [5] => 1 )

Sorting Associative Arrays in Ascending Order By Value

The asort() function sorts the elements of an associative array in ascending order according to the value. It works just like sort(), but it preserves the association between keys and its values while sorting.

<?php
// Define array
$age = array("Peter"=>20, "Harry"=>14, "John"=>45, "Clark"=>35);
 
// Sorting array by value and print
asort($age);
print_r($age);
?>

This print_r() statement gives the following output:

Array ( [Harry] => 14 [Peter] => 20 [Clark] => 35 [John] => 45 )

Sorting Associative Arrays in Descending Order By Value

The arsort() function sorts the elements of an associative array in descending order according to the value. It works just like rsort(), but it preserves the association between keys and their values while sorting.

<?php
// Define array
$age = array("Peter"=>20, "Harry"=>14, "John"=>45, "Clark"=>35);
 
// Sorting array by value and print
arsort($age);
print_r($age);
?>

This print_r() statement gives the following output:

Array ( [John] => 45 [Clark] => 35 [Peter] => 20 [Harry] => 14 )

---

Sorting Associative Arrays in Ascending Order By Key

The ksort() function sorts the elements of an associative array in ascending order by their keys. It preserves the association between keys and its values while sorting, same as asort() function.

<?php
// Define array
$age = array("Peter"=>20, "Harry"=>14, "John"=>45, "Clark"=>35);
 
// Sorting array by key and print
ksort($age);
print_r($age);
?>>

This print_r() statement gives the following output:

Array ( [Clark] => 35 [Harry] => 14 [John] => 45 [Peter] => 20 )

---

Sorting Associative Arrays in Descending Order By Key

The krsort() function sorts the elements of an associative array in descending order by their keys. It preserves the association between keys and its values while sorting, same as arsort() function.

<?php
// Define array
$age = array("Peter"=>20, "Harry"=>14, "John"=>45, "Clark"=>35);
 
// Sorting array by key and print
krsort($age);
print_r($age);
?>

This print_r() statement gives the following output:

Array ( [Peter] => 20 [John] => 45 [Harry] => 14 [Clark] => 35 )