Add order column to array to indicate rank from oldest to youngest

In PHP7, If I have this array:

$array = [
    ["name" => "Jon", "age" => 44],
    ["name" => "Bob", "age" => 32],
    ["name" => "Jim", "age" => 103],
    ["name" => "Ted", "age" => 19]
];

What is the most elegant way to process this array to add an extra column indicating who is the oldest to who is the youngest like so…

[
    ["name" => "Jon", "age" => 44, "order" => 2],
    ["name" => "Bob", "age" => 32, "order" => 3],
    ["name" => "Jim", "age" => 103, "order" => 1],
    ["name" => "Ted", "age" => 19, "order" => 4]
]

Answer

Without a point of reference to determine which is the oldest user you’re stuck either doing a multi loop comparison or a sort then insert.

A Multi loop comparasin would look something like

<?php
$array = [
  ["name" => "Jon", "age" => 44],
  ["name" => "Bob", "age" => 32],
  ["name" => "Jim", "age" => 103],
  ["name" => "Ted", "age" => 19]
];

$count = count($array);

for($index = 0; $index < $count; ++$index) {
  $order = 1;
  $age = $array[$index]["age"];
  for($index2 = 0; $index2 < $count; ++$index2) {
    if($array[$index2]["age"] > $age) {
      ++$order;
    }
  }

  $array[$index]["order"] = $order;
}

echo "<pre>";
var_dump($array);
echo "</pre>";

Sort then insert would involve array_walk and uasort

From the docs

<?php
$fruits = array("d" => "lemon", "a" => "orange", "b" => "banana", "c" => "apple");

function test_alter(&$item1, $key, $prefix)
{
  $item1 = "$prefix: $item1";
}

function test_print($item2, $key)
{
  echo "$key. $item2<br />n";
}

echo "Before ...:n";
array_walk($fruits, 'test_print');

array_walk($fruits, 'test_alter', 'fruit');
echo "... and after:n";

array_walk($fruits, 'test_print');

and docs

<?php
// Comparison function
function cmp($a, $b) {
  if ($a == $b) {
    return 0;
  }
  return ($a < $b) ? -1 : 1;
}

// Array to be sorted
$array = array('a' => 4, 'b' => 8, 'c' => -1, 'd' => -9, 'e' => 2, 'f' => 5, 'g' => 3, 'h' => -4);
print_r($array);

// Sort and print the resulting array
uasort($array, 'cmp');
print_r($array);

so for your example it would be something like this:

<?php
function walkFunc(&$item, $key) {
  $item["order"] = $key + 1;
}

// as @waterloomatt mentioned the Spaceship operator is meant for this
function sortComp($a, $b) {
  return ($a["age"] <=> $b["age"]) * -1;
}

$array = [
  ["name" => "Jon", "age" => 44],
  ["name" => "Bob", "age" => 32],
  ["name" => "Jim", "age" => 103],
  ["name" => "Ted", "age" => 19]
];

uasort($array, 'sortComp');
array_walk($array, 'walkFunc');

echo "<pre>";
var_dump($array);
echo "</pre>";