Laravel 为什么我得到的是整数而不是数组？

我正在尝试将

$user\u id

推入一个数组并将其存储在数据库中

但是当我

dd（$children）

时，我得到的是一个整数值，而不是一个数组。我做错了什么

if($user->hasRole(['guardian','learner'])){
    $user_id = $user->id;
    $db =  Auth::user()->related;
    $children = array_push($db, $user_id);
    dd($children);

    return redirect()
        ->route('parent-child.index')
        ->with('message', $user->name . ' has been added Successfully');
}

---

请尝试以下代码：

if($user->hasRole(['guardian','learner'])){
    $db = []; //declare $db as an array
    $user_id = $user->id;
    $db =  Auth::user()->related;
    array_push($db, $user_id);
    $children = $db;
    dd($children);

    return redirect()
        ->route('parent-child.index')
        ->with('message', $user->name . ' has been added Successfully');
}

---

将子项定义为代码上方的数组，然后再次选中$children=[]；这行是错误的：$children=array\u push（$db，$user\u id）；将其更改为：array\u push（$children，$user\u id）；