Function to sort multidimensional array by a value

[doddsey_65]

Sorry for being in the wrong forum but I couldn't post in the Code Snippets section.

 

Here is a quick function that will sort a multidimensional array by a given value

function subval_sort(array $array, $subkey, $reverse = false)
{
	if (empty($array))
	{
		return array();
	}

	$temp_array = array();

	foreach ($array as $key => $value)
	{
		$temp_array[$key] = strtolower($value[$subkey]);
	}
		
	if ($reverse)
	{
		arsort($temp_array);
	}
	else
	{
		asort($temp_array);	
	}

	$_array = array();

	foreach ($temp_array as $key => $value)
	{
		$_array[] = $array[$key];
	}
	
	return $_array;
}

It can be used as such:

$array = [
    0 => [
        'value' => 6
    ],
    1 => [
        'value' => 2
    ],
    2 => [
        'value' => 1
    ]
]

$array = subval_sort($array, 'value');

This would return:

[
    0 => [
        'value' => 1
    ],
    1 => [
        'value' => 2
    ],
    2 => [
        'value' => 6
    ]
]

And it can be reversed by specifying a third parameter (bool)

$array = subval_sort($array, 'value', true);

[Strider64]

I'm confused, couldn't you just do the following?

function sort_by_value($x, $y) {
    return ($x['value'] > $y['value']);
}

uasort($array, 'sort_by_value');

[Barand]

the function should be

function sort_by_value($x, $y) {
    return ($x['value'] - $y['value']);
}

a sort function needs to return -, 0 or + values

[Strider64]

Your not returning anything, you're sorting a multidimensional array.

 

The following works perfectly fine:

<?php

$students = array(
	256 => array('name' => 'Jon', 'score' => 98.5),
	2 => array('name' => 'Vance', 'score' => 85.1),
	9 => array('name' => 'Stephen', 'score' => 94.0),
	364 => array('name' => 'Steve', 'score' => 85.1),
	68 => array('name' => 'Rob', 'score' => 74.6)
);

function score_sort($x, $y) {
	return ($x['score'] < $y['score']);
}

// Print the array as is:
echo '<h2>Array As Is</h2><pre>' . print_r($students, 1) . '</pre>';

// Sort by score:
uasort($students, 'score_sort');
echo '<h2>Array Sorted By Score</h2><pre>' . print_r($students, 1) . '</pre>';

[kicken]

Your not returning anything, you're sorting a multidimensional array.

Yes, your sort function does return something, hence the return keyword. What was being pointed out to you is that using < returns a true/false boolean, but what the function is supposed to return is a a number <0, =0, or >0.

The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second.

The following works perfectly fine:

Just by luck. The code is still incorrect.