<?php
$users = [
    ['id' => 1, 'name' => 'Alice', 'role' => 'admin'],
    ['id' => 2, 'name' => 'Bob', 'role' => 'editor'],
    ['id' => 3, 'name' => 'Charlie', 'role' => 'admin'],
    ['id' => 4, 'name' => 'David', 'role' => 'viewer'],
    ['id' => 5, 'name' => 'Eve', 'role' => 'editor'],
];

$groupedUsers = [];

// Group users by their 'role' using a foreach loop
foreach ($users as $user) {
    $role = $user['role'];
    if (!isset($groupedUsers[$role])) {
        $groupedUsers[$role] = [];
    }
    $groupedUsers[$role][] = $user;
}

echo "Users Grouped by Role (foreach loop):
";
print_r($groupedUsers);

// Another approach using array_reduce for grouping
$groupedUsersReduced = array_reduce($users, function ($carry, $item) {
    $role = $item['role'];
    // Initialize the sub-array if it doesn't exist
    if (!isset($carry[$role])) {
        $carry[$role] = [];
    }
    $carry[$role][] = $item;
    return $carry;
}, []); // Initial accumulator value is an empty array

echo "
Users Grouped by Role (array_reduce):
";
print_r($groupedUsersReduced);