您每次都在重新声明整个数组，而不是添加整个数组，而是使用以下声明:

You're redeclaring the entire array each time rather than adding to it, use this instead:

foreach($genre as $g)
{
    $array['music'][] = $m->where('mu_id', $g)->get();
}

甚至更好，更少的查询:

Or even better, less queries:

$array['music'] = $m->where_in('mu_id', $genre)->get();