我想要一个来自多维数组的键的值数组

array
{
     [0]=>
     {
            [name] = "maulik";
            [roleId] = 34;
     }
     [1]=>
     {
            [name] = "ketan";
            [roleId] = 12;
     }
     [2]=>
     {
            [name] = "nitish";
            [roleId] = 40;
     }
     [3]=>
     {
            [name] = "hiren";
            [roleId] = 24;
     }
}

$roleIds = array();
foreach($users as $user)
{
    $roleIds[] = $user['roleId'];
}

function getRoleIdsAsArray($index)
{
        return $index['roleId'];
}

$roleIds = array_map("getRoleIdsAsArray" , $users);