PHP Array sorting using child nodes?

Question

Ok I have the following array:

Array
(
   [0] => Array
    (
        [id] => 6
        [name] => This Course
        [time] => 1288082700
        [description] => blah blah . 
        [link] => http://this.com/?g=5
        [course] => 22
    )

[1] => Array
    (
        [id] => 2
        [name] => Workshop
        [time] => 1287561600
        [description] => This description
        [link] => http://this.com/?g=5
        [session] => 8
        [course] => 23
        [type] => standard
        [adobelink] => 
    )

)

How can I sort this entire array by using the inner 'time' key ?

Thanks!

Answer 1

Use usort():

This function will sort an array by its values using a user-supplied comparison function. If the array you wish to sort needs to be sorted by some non-trivial criteria, you should use this function.

Example:

function cmp($a, $b) {
    if ($a['time'] == $b['time']) {
        return 0;
    }
    return ($a['time'] < $b['time']) ? -1 : 1;
}

usort($array, 'cmp');

Of course this will fail if an array has no time element. What should happen then depends on your requirements so I will leave the error handling to you ;)

Answer 2

http://dk.php.net/usort

function sortByTime($a, $b)
{
 if ($a['time'] > $b['time'])
 {
  return 1;
 }
 else if ($a['time'] < $b['time'])
 {
  return -1;
 }
 return 0;
}

usort($yourArray, 'sortByTime');

Answer 3

Use PHP usort() function: http://php.net/manual/en/function.usort.php

First, define a function that will decide on compare result for your data structure:

function cmp($a, $b)
{
    if ($a['time'] == $b['time']) {
        return 0;
    }
    return ($a['time'] < $b['time']) ? -1 : 1;
}

Then call usort() and give the nmae of your function to it:

usort($array, "cmp");

You're done!

Answer 4

uasort() will maintain your keys¹.

uasort($a, function($a, $b) {
    $a = $a['time']; // Assuming keys exist
    $b = $b['time'];
    if ($a == $b) {
        return 0;
    } else {
        return $a < $b ? -1 : 1; // Reverse < if sort order is wrong
    }
});

Anonymous function syntax requires PHP 5.3+! Pass the name of the comparison function if <5.3 (see other answers).

¹⁾ In case you care about the keys, too. If not, just use the usort() approach found in abundance above :) The comparison function are basically identical (except for @codaddict's elegant approach).

Answer 5

You can use the usort function as:

function cmp($a,$b) {
        return $a['time'] - $b['time'];
}

usort($arr,'cmp');

Working link