php sorting an array by predefined order

Question

I'm struggling trying to sort an array via the normal functions, i'm sure this needs a custom comparison function but none the less will chuck this out there.

I have an array with 5 elements inside it. I would like the array to sort itself like so, arsort came close but not quite:

4,0,1,2,3

Just to clarify, the position of the array like: $array[0];

I haven't actually looked at array comparison functions before, so a push in the right direction would be most helpful to solve this!

Thanks,

Adam

You can use [`usort()`](http://php.net/usort) to sort an array via a custom comparison function. — Carsten, Mar 08 '13 at 13:23

score 18 · Accepted Answer · edited Mar 29 '17 at 22:06

This method will sort an array using a pre-defined order of keys using uksort

$desiredIndexOrder = array(4 => 1, 0 => 2, 1 => 3, 2 => 4, 3 => 5);

uksort($inputArray, function($a, $b) use ($desiredIndexOrder) {
    return $desiredIndexOrder[$a] > $desiredIndexOrder[$b] ? -1 : 1;
});

Notice the $desiredIndexOrder array is in index => desired sort position format. If you don't want to put your array in that format, you can have it built for you using this:

$desiredIndexOrder = array();

foreach ($desiredKeyOrder as $position=>$key) {
    $desiredIndexOrder[$key] = $position + 1;
}

Where $desiredKeyOrder is the array order of your keys: array(4, 0, 1, 2, 3)

Thanks Colin, this was exactly what I was after. Also using the comparative function answered my question perfectly. — evensis, Mar 08 '13 at 13:42

Nirmal Ram · Answer 2 · 2013-03-08T13:32:06.777

0

Try this

$array = array('t','r','a','c','k');
$keys = '4,0,1,2,3';

$keyArr = explode(',', $keys);
$sarr = array();

foreach ($keyArr as $key)
{
    $sarr[$key] = $array[$key];
}
print_r($sarr);

edited Mar 08 '13 at 13:32

answered Mar 08 '13 at 13:23

Nirmal Ram

1,722
4
25
45

1

Think it might be important to put quotes around your string? Also, this won't work. – Colin M Mar 08 '13 at 13:24

score 0 · Answer 3 · answered Mar 08 '13 at 13:26

0

Try this :

$numbers = array(1,2,3,4,5);
array_unshift($numbers, array_pop($numbers));

echo "<pre>";
print_r($numbers);

Output :

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

answered Mar 08 '13 at 13:26

Prasanth Bendra

31,145
9
53
73

php sorting an array by predefined order

3 Answers3

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