PHP

php implode array

$values = array_map('array_pop', $array);
$imploded = implode(',', $values);

php implode associative array

$users = [
	'user1' => 'user1@example.com',
	'user2' => 'user2@example.com'
];

echo implode(', ',$users);
// "user1@example.com, user2@example.com"