Sort a flat associative array based on another array and preserve keys [duplicate]

Question

I already got this question in Stack Overflow, but sadly it's in javascript - Sort a JavaScript array based on another array

and I want it in PHP

$data = array(
   "item1"=>"1",
   "item2"=>"3",
   "item3"=>"5",
   "item4"=>"2",
   "item5"=>"4"
);

to match the arrangement of this array:

sortingArr = array("5","4","3","2","1");

and the output I'm looking for:

$data = array(
    "item3"=>"5",
    "item5"=>"4",
    "item2"=>"3",
    "item4"=>"2",
    "item1"=>"1"
 );

Answer 1

For a detailed answer, why array_multisort does not match your needs, view this answer, please: PHP array_multisort not sorting my multidimensional array as expected

In short: You want to sort an array based on a predefined order. The Answer is also given over there, but i copied one solution to this answer, too:

Use usort and array_flip, so you be able to turn your indexing array (ValueByPosition) into a PositionByValue Array.

    $data = array(
   "item1"=>"1",
   "item2"=>"3",
   "item3"=>"5",
   "item4"=>"2",
   "item5"=>"4"
);

usort($data, "sortByPredefinedOrder");

function sortByPredefinedOrder($leftItem, $rightItem){
  $order = array("5","4","3","2","1");

  $flipped = array_flip($order);

  $leftPos = $flipped[$leftItem];
  $rightPos = $flipped[$rightItem];
  return $leftPos >= $rightPos;   
}

print_r($data);
// usort: Array ( [0] => 5 [1] => 4 [2] => 3 [3] => 2 [4] => 1 )
// uasort: Array ( [item3] => 5 [item5] => 4 [item2] => 3 [item4] => 2 [item1] => 1 )

However this would require you to predict all possible items inside the predefined order array, or thread other items in an appropriate way.

If you want to maintain the assoc keys, use uasort instead of usort.

Answer 2

Pretty simple ?

$data = array(
   "item1"=>"1",
   "item2"=>"3",
   "item3"=>"5",
   "item4"=>"2",
   "item5"=>"4"
);

$sortingArr = array("5","4","3","2","1");

$result = array(); // result array
foreach($sortingArr as $val){ // loop
    $result[array_search($val, $data)] = $val; // adding values
}
print_r($result); // print results

Output:

Array
(
    [item3] => 5
    [item5] => 4
    [item2] => 3
    [item4] => 2
    [item1] => 1
)

Answer 3

using usort() the right way i think

Sort an array by values using a user-defined comparison function

you can do as follow:

$data = array(
   "item1"=>"1",
   "item2"=>"3",
   "item3"=>"5",
   "item4"=>"2",
   "item5"=>"4"
);

$sortingArr = array("5","4","3","2","1");

$keys = array_flip($sortingArr);

usort($data, function ($a, $b) use ($keys) {
    return $keys[$a] > $keys[$b] ? 1 : -1;
});

print_r($data);

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

live example: https://3v4l.org/75cnu

Answer 4

I'm pretty proud of my solution:

uasort($data, function($a, $b) use ($sortingArr) {  
    return array_search($a, $sortingArr) <=> array_search($b, $sortingArr);
});

Working example: https://3v4l.org/bbIk2

1. It uses uasort to maintain the key-value associations as the OP requested. (unlike @hassan's otherwise elegant solution)
2. It doesn't require that every element in the $data array be present in the sorting array. (like @HamZa's solution)
3. It's brief.
4. It uses the spaceship operator <=> for comparison instead of more verbose logic.

Code:

Answer 5

Look at my following snippet to sort your array based on another array:

$res_arr = array(); 
for ($i = 0; $i < count($sortingArr); $i++) {
     for ($j = 0; $j < count($data); $j++) {
          if($data[$j] == $sortingArr[$i]) {
             $res_arr[] = $data[$j];
             break;
          }
     }
}
// $res_array is your sorted array now

Answer 6

Look at code snippet to make a multidimensional array sort in order of input

$input_format_list = [4, 1];
$data = array(
    "0" => array(
        "School" => array(
            "id" => 1,
             "name" => "ST.ANN'S HIGH SCHOOL",
        )
    ),     
    "1" => array(
        "School" => array(
            "id" => 4,
            "name" => "JYOTI VIDHYA VIHAR",
        )
    )
);   

$result = array(); // result array
foreach($input_format_list as $key => $value){ // loop
    foreach ($data as $k => $val) {
        if ($data[$k]['School']['id'] === $value) {
           $result[$key] = $data[$k];
        }
    }            
}            
return $result;

Answer 7

Take a look at array_multisort. I'm not completely sure how to use it, as I have never found a practical use for it (I prefer to use usort to clearly define my terms), but it might work for you.

Answer 8

<?php 
$data = array(
   "item1"=>"1",
   "item2"=>"3",
   "item3"=>"5",
   "item4"=>"2",
   "item5"=>"4"
);
$result=array_flip($data);

krsort($result);

$result=array_flip($result);

print_r($result);

//use rsort for the index array

$sortingArr = array("5","4","3","2","1");

print_r($sortingArr);

Answer 9

Expanding on the Answer of Andrew, if you want the undefined entries in the sorting array to appear at the end of the output array:

uasort($currentTags, function ($a, $b) use ($sortingArr) {
    if (in_array($a, $sortingArr) && !in_array($b, $sortingArr)) return -1;
    if (!in_array($a, $sortingArr) && in_array($b, $sortingArr)) return 1;
    if (!in_array($b, $sortingArr)) return -1;
    return array_search($a, $sortingArr) <=> array_search($b, $sortingArr);
});