Every time I need to sort a multi-dimensional array in PHP, I have to look it up. It's not quite as quick and easy to look up as most things, so I'm going to blog a quick example.

Here's a simple array of users:

1. <?php
2.  
3. $users = array();
4.  
5. $users[] = array('username' => 'shiflett', 'name' => 'Chris Shiflett');
6. $users[] = array('username' => 'dotjay', 'name' => 'Jon Gibbins');
7. $users[] = array('username' => 'a', 'name' => 'Andrei Zmievski');
8.  
9. ?>

There are a few different ways to create this array. Here's the output of print_r($users), so you clearly understand the structure:

1. Array
2. (
3.     [0] => Array
4.         (
5.             [username] => shiflett
6.             [name] => Chris Shiflett
7.         )
8.  
9.     [1] => Array
10.         (
11.             [username] => dotjay
12.             [name] => Jon Gibbins
13.         )
14.  
15.     [2] => Array
16.         (
17.             [username] => a
18.             [name] => Andrei Zmievski
19.         )
20.  
21. )

If I want to sort by username, I first create a separate array of usernames:

1. <?php
2.  
3. $usernames = array();
4.  
5. foreach ($users as $user) {
6.     $usernames[] = $user['username'];
7. }
8.  
9. ?>

I then use array_multisort():

1. <?php
2.  
3. array_multisort($usernames, SORT_ASC, $users);
4.  
5. ?>

Here's the output of print_r($users) after sorting by username:

1. Array
2. (
3.     [0] => Array
4.         (
5.             [username] => a
6.             [name] => Andrei Zmievski
7.         )
8.  
9.     [1] => Array
10.         (
11.             [username] => dotjay
12.             [name] => Jon Gibbins
13.         )
14.  
15.     [2] => Array
16.         (
17.             [username] => shiflett
18.             [name] => Chris Shiflett
19.         )
20.  
21. )

To sort the array by name instead, I'd do something very similar:

1. <?php
2.  
3. $names = array();
4.  
5. foreach ($users as $user) {
6.     $names[] = $user['name'];
7. }
8.  
9. array_multisort($names, SORT_ASC, $users);
10.  
11. ?>

Here's the output of print_r($users) after sorting by name:

1. Array
2. (
3.     [0] => Array
4.         (
5.             [username] => a
6.             [name] => Andrei Zmievski
7.         )
8.  
9.     [1] => Array
10.         (
11.             [username] => shiflett
12.             [name] => Chris Shiflett
13.         )
14.  
15.     [2] => Array
16.         (
17.             [username] => dotjay
18.             [name] => Jon Gibbins
19.         )
20.  
21. )

There are many more uses of array_multisort(), and there are many other useful sorting functions. Please feel free to share some of your favorites in the comments.

Update: If your array isn't too big, and especially if you find it easier to understand, you might prefer usort(). Thanks to Franco Zeoli for this example:

1. <?php
2.  
3. // Sort the array by username.
4. usort($users, function ($a, $b) {
5.                   return strcmp($a['username'], $b['username']);
6.               });
7.  
8. ?>