以数据库事务为例：
    方法1:

    1. // Should contain any messages to pass back to the user
    2. $results = [];
    4. // Contains the total records inserted
    5. $total = 0;
    7. DB::transaction(function() use($csv_file, &$results, &$total) {
    9.     // Some Code ...
    11.     $total++;
    12.     $results[] = 'Row 10 has some weird data...';
    13. });
    15. return view('plan.import')
    16.     ->with('results', $results)
    17.     ->with('total', $total);

    函数内部所做的更改将反映在变量中，因为&创建变量的引用（传递变量引用）而不是按值传递变量。检查通过参考手册传递。

    方法2:

    // Should contain any messages to pass back to the user
$results = [];

// Contains the total records inserted
$total = 0;

$array = DB::transaction(function() use($csv_file, $results, $total) {

    // Some Code ...

    $total++;
    $results[] = 'Row 10 has some weird data...';
    return compact('total', 'results');
});

return view('plan.import')
->with('results', $array['results'])
->with('total', $array['total']);

    从闭包内部返回变量。