Sorting an Array in PHP

By: David Sklar  

You want to sort an array in a specific way.

To sort an array using the traditional definition of sort, use sort():

$states = array('Delaware', 'Pennsylvania', 'New Jersey');

To sort numerically, pass SORT_NUMERIC as the second argument to sort( ).

$scores = array(1, 10, 2, 20);
sort($scores, SORT_NUMERIC);

This resorts the numbers in ascending order (1, 2, 10, 20) instead of lexicographical order (1, 10, 2, 20).

The sort() function doesn't preserve the key/value association between elements; instead, entries are reindexed starting at 0 and going upward. (The one exception to this rule is a one-element array; its lone element doesn't have its index reset to 0. This is fixed as of PHP 4.2.3.)

To preserve the key/value links, use asort( ). The asort( ) function is normally used for associative arrays, but it can also be useful when the indexes of the entries are meaningful:

$states = array(1 => 'Delaware', 'Pennsylvania', 'New Jersey');

while (list($rank, $state) = each($states)) {
    print "$state was the #$rank state to join the United States\n";


Use natsort( ) to sort the array using a natural sorting algorithm. Under natural sorting, you can mix strings and numbers inside your elements and still get the right answer.

$tests = array('test1.php', 'test10.php', 'test11.php', 'test2.php');

The elements are now ordered: 'test1.php', 'test2.php', 'test10.php', and 'test11.php'. With natural sorting, the number 10 comes after the number 2; the opposite occurs under traditional sorting. For case-insensitive natural sorting, use natcasesort( ).

To sort the array in reverse order, use rsort( )or arsort( ), which is like rsort( ) but also preserves keys. There is no natrsort( ) or natcasersort( ). You can also pass SORT_NUMERIC into these functions.

Archived Comments

Most Viewed Articles (in PHP )

The new keyword and constructors in PHP

Input Validation in PHP

Convert a hex string into a 32-bit IEEE 754 float number in PHP

Using Sessions in PHP

Multiple File Upload in PHP using IFRAME

Exception in module wampmanager.exe at 000F15A0 in Windows 8

PHP 5.1.4 INSTALLATION on Solaris 9 (Sparc)

Installing PHP and MySQL in windows, mac and linux

Building PHP 5.x with Apache2 on SuSE Professional 9.1/9.2

Installing PHP 5.x with Apache 2.x on HP UX 11i and configuring PHP 5.x with Oracle 9i

Cannot load /usr/local/apache/libexec/ into server:

Setting up PHP in Windows 2003 Server IIS7, and WinXP 64

error: "Service Unavailable" after installing PHP to a Windows XP x64 Pro

Function to sort array by elements and count of element in PHP

Function to convert strings to strict booleans in PHP

Latest Articles (in PHP)

Comment on this tutorial