php - sort array by custom criteria - php

Question

I have an array of objects:
object1->
name="Name1"
key="key1"
object2->
name="Name2"
key="key2"
object3->
name="Name3"
key="key3"
and an array of priority keys:
$keys = ["key3", "key1"];
I need to sort the array of objects based on priority keys, so the result should be:
object3:
name="Name3"
key="key3"
object1->
name="Name1"
key="key1"
object2:
name="Name2"
key="key2"
What is the best way to do it?

Answer 1

The idea is to add a priority as integer, and sort the array from the highest integer to the lowest using usort()
for example you have this data
<?php
$data = [];
$data[0] = new stdClass;
$data[0]->name = "name1";
$data[0]->key = 'key1';
$data[1] = new stdClass;
$data[1]->name = "name2";
$data[1]->key = 'key2';
$data[2] = new stdClass;
$data[2]->name = "name3";
$data[2]->key = 'key3';
$keys = ["key3", "key1"];
you can sort it this way
function sortByPriority($data , $keys){
$priority = array();
$i = count($keys);
foreach ($keys as $key => $value) {
$i--;
$priority[$value] = $i;
}
usort($data, function($a, $b) use($priority){
$a = isset($priority[$a->key]) ? $priority[$a->key] : -1;
$b = isset($priority[$b->key]) ? $priority[$b->key] : -1;
return $b - $a;
});
return $data;
}
var_dump(sortByPriority($data, $keys));
sample output
array (size=3)
0 =>
object(stdClass)[3]
public 'name' => string 'name3' (length=5)
public 'key' => string 'key3' (length=4)
1 =>
object(stdClass)[1]
public 'name' => string 'name1' (length=5)
public 'key' => string 'key1' (length=4)
2 =>
object(stdClass)[2]
public 'name' => string 'name2' (length=5)
public 'key' => string 'key2' (length=4)

Answer 2

Once you prepare your priority lookup array it is merely a matter of passing it into usort()'s scope and either using the related priority value or if the key property's value is not in the priority array, then use the fallback value. Readable, direct, and concise.
Code: (Demo)
$objects = [
(object)["name" => "Name1", "key" => "key1"],
(object)["name" => "Name2", "key" => "key2"],
(object)["name" => "Name3", "key" => "key3"],
];
$keys = ["key3", "key1"];
$lookup = array_flip($keys);
$fallback = count($keys);
usort($objects, function($a, $b) use ($lookup, $fallback) {
return ($lookup[$a->key] ?? $fallback) <=> ($lookup[$b->key] ?? $fallback);
});
var_export($objects);
Output:
array (
0 =>
(object) array(
'name' => 'Name3',
'key' => 'key3',
),
1 =>
(object) array(
'name' => 'Name1',
'key' => 'key1',
),
2 =>
(object) array(
'name' => 'Name2',
'key' => 'key2',
),
)
From PHP7.4, the syntax can be further condensed and the use() declaration omitted. (Demo)
usort($objects, fn($a, $b) => ($lookup[$a->key] ?? $fallback) <=> ($lookup[$b->key] ?? $fallback));

Answer 3

There is the function usort in PHP do what you need :
usort( $your_array), "sort_function");
sort_function( $a, $b) {
// your sort logic
}