php - laravel 如何从多个表中获取列值？

Question

如何代表第一个表的列特定 id 获取第二个表的列值，就像在这段代码中，它从同一个表获取值，但我想更改它以代表从其他表获取值用户表的列 ID。

    $user = User::find(Auth::id());
    $ref_id = $user->referrer_id;
    $ref_user = User::find($ref_id);
    $new_Balance = $ref_user['balance']  = $ref_user['balance'] + 
    $comission->update_commision_sponsor;
    $ref_user->save();

我希望它是这样的:

    $user = User::find(Auth::id());
    $ref_id = $user->referrer_id;
    $ref_user = User::find($ref_id); (here I want to assign second table where the referrer_id column dose not exist.)
    $new_Balance = $ref_user['balance (here I want second table's column "earning")']  = $ref_user['balance(here I want second table's column "earning")'] + $comission->update_commision_sponsor;
    $ref_user->save();

Answer 1

if 条件可能有帮助

$user = User::find(Auth::id());
$ref_id = $user->referrer_id;

if($ref_id == null){
    $anotherTable = AnohterTable::find($id);
    $ref_id == $anotherTable->another_column;
}

$ref_user = User::find($ref_id); (here I want to assign second table where the referrer_id column dose not exist.)
$new_Balance = $ref_user['balance (here I want second table's column "earning")']  = $ref_user['balance(here I want second table's column "earning")'] + $comission->update_commision_sponsor;
$ref_user->save();