Sort array by non-alphabetical, user defined string values

Question

I want to sort an array in a complicated way and am not sure how to go about it. Here is a rough idea of the data I'm working with:

[
  { target: random.text.cpu-pct-0, otherData[...] },
  { target: random.text.cpu-pct-1, otherData[...] },
  { target: random.text.cpu-pct-2, otherData[...] },
  { target: random.text.example-0, otherData[...] },
  { target: random.text.example-1, otherData[...] },
  { target: random.text.memory, otherData[...] },
  ...
]

I want all the objects with a target that includes the string cpu-pct to come first, then the objects with a target that includes the string memory, then example. This array could have any number of items, so re-sorting by index won't work. There could be 1 object with a target that includes cpu-pct, or there could be 50+. Same goes for the other strings I'm sorting by.

I thought about looping over the original array, checking if the desired string exists, saving the matching objects to new arrays for each target I'm looking for, then merging the arrays at the end. I think that would work, but I'd imagine there is a better, more efficient solution, probably using usort, but I'm at a loss. Any ideas?

Answer 1

usort is definitely the way to go. Here's a fairly generalised way of doing it, you can expand the $ranks array to include other terms to sort against if you like.

$a = json_decode('[
  { "target": "random.text.cpu-pct-0", "otherData": [1, 2, 3] },
  { "target": "random.text.cpu-pct-1", "otherData": [2, 2, 3] },
  { "target": "random.text.cpu-pct-2", "otherData": [3, 2, 3] },
  { "target": "random.text.example-0", "otherData": [4, 2, 3] },
  { "target": "random.text.example-1", "otherData": [5, 2, 3] },
  { "target": "random.text.memory", "otherData": [6, 2, 3] } ]');

$ranks = array('example' => 0, 'memory' => 1, 'cpu-pct' => 2);

function rank($obj) {
    global $ranks;

    foreach ($ranks as $key => $value) {
        if (strpos($obj->target, $key) !== false) return $value;
    }
    // sort anything that doesn't match last
    return -1;
}

function cmp($a, $b) {
    return rank($b) - rank($a);
}

usort($a, "cmp");

print_r($a);

Output:

Array
(
    [0] => stdClass Object
        (
            [target] => random.text.cpu-pct-0
            [otherData] => Array
                (
                    [0] => 1
                    [1] => 2
                    [2] => 3
                )

        )

    [1] => stdClass Object
        (
            [target] => random.text.cpu-pct-1
            [otherData] => Array
                (
                    [0] => 2
                    [1] => 2
                    [2] => 3
                )

        )

    [2] => stdClass Object
        (
            [target] => random.text.cpu-pct-2
            [otherData] => Array
                (
                    [0] => 3
                    [1] => 2
                    [2] => 3
                )

        )

    [3] => stdClass Object
        (
            [target] => random.text.memory
            [otherData] => Array
                (
                    [0] => 6
                    [1] => 2
                    [2] => 3
                )

        )

    [4] => stdClass Object
        (
            [target] => random.text.example-0
            [otherData] => Array
                (
                    [0] => 4
                    [1] => 2
                    [2] => 3
                )

        )

    [5] => stdClass Object
        (
            [target] => random.text.example-1
            [otherData] => Array
                (
                    [0] => 5
                    [1] => 2
                    [2] => 3
                )

        )

)

If you want to further sort on the value after the keyword, you could append that to the ranking value and then sort on the combined value e.g.

$ranks = array('cpu-pct', 'memory', 'example');

function rank($obj) {
    global $ranks;

    foreach ($ranks as $key => $value) {
        if (preg_match("/$value(.*)$/", $obj->target, $matches))
            return $key . $matches[1];
    }
    // sort anything that doesn't match last
    return 'z';
}

function cmp($a, $b) {
    return strcmp(rank($a), rank($b));
}

usort($a, "cmp");

If you had more than 10 strings to sort by, you would need to change the return value from rank to sprintf('%02d', $key) . $matches[1] to ensure sorting worked properly (replace 02 with as many digits as necessary to ensure you can represent all the sort strings in that many digits).