Solution to coding assignment

index.php

<?php

include_once 'json.php';

$people = json_decode($people, true);

$data = $people['data'];

$email = '';

usort($data, 'compare');

function compare ($prev, $next) {
    if ($prev['age'] == $next['age']) {
        return 0;
    }
    
    return ($prev['age'] > $next['age']) ? -1 : 1;
}

$data = array_map(function ($obj) use (&$email) {
    $email .= "{$obj['email']},";

    $obj['name'] = "{$obj['first_name']} {$obj['last_name']}";

    return $obj;
}, $data);

$email = trim($email, ',');

json.php

<?php

$people = '{"data":[{"first_name":"jake","last_name":"bennett","age":31,"email":"[email protected]","secret":"VXNlIHRoaXMgc2VjcmV0IHBocmFzZSBzb21ld2hlcmUgaW4geW91ciBjb2RlJ3MgY29tbWVudHM="},{"first_name":"jordon","last_name":"brill","age":85,"email": "[email protected]","secret":"YWxidXF1ZXJxdWUuIHNub3JrZWwu"}]}';