Question

我有一个PDO对象连接到数据库，我有5个类需要数据库连接的方法。对于我正在构建$db的每个班级。这是真的方法吗？如果没有，我该怎么办？

try {
    $config['db'] = array(
        'host'     => 'localhost',
        'username' => 'xxxxxx',
        'password' => 'xxxxxx',
        'dbname'   => 'table_name'
    );
    $db = new PDO('mysql:host=' . $config['db']['host'] . ';dbname=' . $config['db']['dbname'], $config['db']['username'], $config['db']['password'], array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8"));
} catch (Exception $e) {
    echo "!";
}

//classA
class ClassA{
    private $db;
    public function __construct(PDO $db){
        $this->db = $db;
    }

    public function methodA1($someId){
        $res = $this->db->query("SELECT * FROM bla WHERE id = $someId ");
        return $res->fetchAll(PDO::FETCH_ASSOC);
    }
}

//classB
class ClassB{
    private $db;
    public function __construct(PDO $db){
        $this->db = $db;
    }

    public function methodB1($someId){
        $res = $this->db->query("SELECT * FROM bla WHERE id = $someId ");
        return $res->fetchAll(PDO::FETCH_ASSOC);
    }
}

然后我为这些类创建新对象，如

$classAObject = new ClassA($db);
$classBObject = new ClassB($db);

在创建对象时，我是否连接过DB 2次？

Answer 1

它连接一次。

您正在使用相同的PDO对象，因此它只会使用您在包含文件时初始化的对象。

我建议你把它变成一个单例，这样当你使用PDO对象时，你总是得到一个已被初始化的对象，将被所有连接使用。

模型类

class Model {
    private $_mysql;

    public function __construct() {
        //Get "singleton" instance of the DatabaseConnector (shared between all Models)
        $this->_mysql = DatabaseConnector::getInstance();
    }
}

DatabaseConnector类

class DatabaseConnector extends Singleton {
    private $_mysql;

    public function __construct() {
        $this->_mysql = new PDO(...);
    }

    public function beginTransaction() { 
        return $this->_mysql->beginTransaction();
    }

    public function commit() { 
        return $this->_mysql->commit();
    }

    public function rollback() { 
        return $this->_mysql->rollback();
    }
}

Singleton类

class Singleton
{
 /**
 * @var Singleton The reference to *Singleton* instance of this class
 */
 private static $instance;

 /**
 * Returns the *Singleton* instance of this class.
 *
 * @return Singleton The *Singleton* instance.
 */
public static function getInstance()
{
    if (null === static::$instance) {
        static::$instance = new static();
    }

    return static::$instance;
}

/**
 * Protected constructor to prevent creating a new instance of the
 * *Singleton* via the `new` operator from outside of this class.
 */
protected function __construct(){}

/**
 * Private clone method to prevent cloning of the instance of the
 * *Singleton* instance.
 *
 * @return void
 */
private function __clone(){}

/**
 * Private unserialize method to prevent unserializing of the *Singleton*
 * instance.
 *
 * @return void
 */
private function __wakeup(){}

}

您可以查看此详细信息singleton

此外，您最好将文件分开，在一个文件中只有一个单独的类。

Answer 2

如果你传递每个对象对同一个$db对象的引用，你所做的就是初始化对象的属性，PDO $db等于传递的PDO对象，所以不，我不要相信你会不止一次连接到数据库。

将不止一个__construct（$ db）尝试多个连接到DB？

2 个答案: