在php中返回Closure的结果？

Question

Somewhere in my __call magic method I'm invoking transactional, accepting a Closure:

try {
    $that = $this
    $this->conn->transactional(function ($conn) use ($that, $realMethod) {
        $result = call_user_func([$that, $realMethod], $conn);
        $this->conn->exec('SET foreign_key_checks = 1');
    });
} catch (\Exception $e) {
    $this->conn->exec('SET foreign_key_checks = 1');

    throw $e;
}

Is there any way to return $result from inside the Closure (or using pass by reference, etc.)?

Method $conn->transactional is not under my control:

public function transactional(Closure $func)
{
    $this->beginTransaction();
    try {
        $func($this);
        $this->commit();
    } catch (Exception $e) {
        $this->rollback();
        throw $e;
    }
}

Answer 1

Sure there is -- create a local variable inside the try block and capture it by reference:

$result = null;
$that = $this;
$this->conn->transactional(function ($conn) use ($that, $realMethod, &$result) {
    $result = call_user_func([$that, $realMethod], $conn);
    $this->conn->exec('SET foreign_key_checks = 1');
});

return $result;

Of course this assumes that transactional will call its argument on the spot, since that's the case indeed we can all be happy.