如何在Laravel 5上获取有关系的字段的名称？

use Illuminate\Database\Eloquent\Model;

class User extends Model
{
    public function posts()
    {
        return $this->hasMany(Post::class);
    }
}

class Post extends Model
{
    public function user()
    {
        return $this->belongsTo(User::class);
    }
}

$user = User::find(1);
$relations = $user->getRelations();

foreach ($relations as $relationName => $relation) {
    $foreignKey = $relation->getQualifiedForeignKeyName();
    echo "关联关系名称: $relationName\n";
    echo "关联模型的外键字段名称: $foreignKey\n";
}