case_study_08.php

<?php

$users = [
    '[email protected]' => 'Adimas Lutfi Wicaksono',
    '[email protected]' => 'Salman Alfarisi',
    '[email protected]' => 'Muhammad Sholeh',
    '[email protected]' => 'Yadi Cahyadi',
    '[email protected]' => 'Maya Maulani',
];

foreach ($users as $key => $value)
{
	$emails[] = $key;
}

print_r($emails);