functions.php

// This function will sort the records by age desc
function sortByAgeDesc($arrayOfObjects) {
    usort($arrayOfObjects, function($a, $b) {
        return $b['age'] <=> $a['age'];
    });
    return $arrayOfObjects;

}


// This function will return just the ages:

function getAges($arrayOfObjects) {

  return array_map(function($item) {
    return (int)$item['age'];
   }, $arrayOfObjects);
   
}


// This function converts to Array of arrays while keeping the age as key

function convertToArrayByAgeKey($arrayOfObjects){
$return = [];
foreach ($arrayOfObjects as $object){
  $return[$object['age']] = $item;
}
return $return;
}