Recommended way for passing data connection to a PHP class / method?

Question

As of right now I have a database connection string included at the top of each of my pages. I'm then passing my database connection to the methods in my class like this:

public function select($db) {
  //Code here
}

Code on page:

$login_user->select($db);

My thought is that if I ever want to query a different database I can just create a new connection string in my include file called $db2 and then I just pass that value instead of $db.

Is this a standard way of doing this or do you have a different recommendation?

Answer 1

将连接字符串传递给您的类有很多缺点并且没有任何好处。您的方向是正确的，但您希望传递数据库对象而不是连接字符串。

依赖注入是让类访问数据库的好方法，这只是意味着将依赖项（即数据库对象）传递给需要它们的对象，而不是对象本身从某种全局变量获取依赖项。

我建议您使用setDb()类上的方法来传递数据库对象，然后将其存储为属性以供任何内部使用。

例如，假设您已$db在初始化脚本中创建了数据库对象：

class SomeClass
{
    protected $db;

    public function setDb($db)
    {
        $this->db = $db;
    }

    public function something()
    {
        // do some query on the database using $this->db
    }
}

$obj = new SomeClass();
$obj->setDb($db);

$obj->something();

DI 为您带来了您提到的好处：能够轻松切换数据库，而无需在您的方法中做大量工作。还有其他好处，即易于测试。