Question

下面是我到目前为止提出的数据库连接类，但我将通过扩展PDO类本身来改进它，

<?php
class database
{
    protected $connection = null;

    #make a connection
    public function __construct($hostname,$dbname,$username,$password)
    {
        try 
        {
            # MySQL with PDO_MYSQL  
            $this->connection = new PDO("mysql:host=$hostname;dbname=$dbname", $username, $password);
            $this->connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); 
        }
        catch (PDOException $e) 
        {
            $this->connection = null;
            die($e->getMessage());
        }
    }

    #get the number of rows in a result
    public function num_rows($query)
    {
        # create a prepared statement
        $stmt = $this->connection->prepare($query);

        if($stmt) 
        {
            # execute query 
            $stmt->execute();

            return $stmt->rowCount();
        } 
        else
        {
            return self::get_error();
        }
    }

    #display error
    public function get_error() 
    {
        $this->connection->errorInfo();
    }

    # closes the database connection when object is destroyed.
    public function __destruct()
    {
        $this->connection = null;
    }
}
?>

扩展课程，

class database extends PDO
{

    #make a connection
    public function __construct($hostname,$dbname,$username,$password)
    {
        parent::__construct($hostname,$dbname,$username,$password);

        try 
        { 
            $this->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); 
        }
        catch (PDOException $e) 
        {
            die($e->getMessage());
        }
    }

    #get the number of rows in a result
    public function num_rows($query)
    {
        # create a prepared statement
        $stmt = parent::prepare($query);

        if($stmt) 
        {
            # execute query 
            $stmt->execute();

            return $stmt->rowCount();
        } 
        else
        {
            return self::get_error();
        }
    }

    #display error
    public function get_error() 
    {
        $this->connection->errorInfo();
    }

    # closes the database connection when object is destroyed.
    public function __destruct()
    {
        $this->connection = null;
    }
}

这就是我实例化类的方法，

# the host used to access DB
define('DB_HOST', 'localhost');

# the username used to access DB
define('DB_USER', 'root');

# the password for the username
define('DB_PASS', 'xxx');

# the name of your databse 
define('DB_NAME', 'db_2011'); 

include 'class_database.php';

$connection = new database(DB_HOST,DB_NAME,DB_USER,DB_PASS);
$sql = "
    SELECT *
    FROM root_contacts_cfm
    ORDER BY cnt_id DESC
    ";

$connection->num_rows($sql);

但是当我调用这个扩展的pdo类时，我有错误，

警告：PDO :: __ construct（）需要   参数4为数组，给定字符串   在C：\ wamp \ www \ xx \ class_database.php中   在xx线上

致命错误：调用成员函数   setAttribute（）在非对象中   C：\ wamp \ www \ xx \ class_database.php on   第xx行

我在网上做了一些研究，我找到了扩展pdo的基本结构，但我不明白......

class myPDO extends PDO
{
   public function __construct($dsn, 
                               $username=null, 
                               $password=null, 
                               $driver_options=null)
   {
      parent::__construct($dsn, $username, $password, $driver_options);
   }

   public function query($query)
   {
      $result = parent::query($query);
      // do other stuff you want to do here, then...
      return($result);
   }
}

$ds n变量是什么？如何将$hostname变量传递给扩展的pdo类？

另一个问题：如何在扩展的pdo类中创建显示错误的方法？如何在扩展的pdo类中关闭连接？

从mysqli转到pdo是如此困难！

感谢。

Answer 1

我会专注于课程需要做的事情，而不是试图重新编写PDO。我有同样的想法，因为我虽然它会简化和流水线代码，但事实并非如此。您最终会花费更多时间来研究如何间接与PDO接口。

Answer 2

$ dsn是数据源名称。它会为您处理您的主机名。你这样使用它：

$dsn = 'mysql:dbname=YOUR_DB_NAME;host=YOUR_HOSTNAME'

使用行$this->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);您设置了在发生错误时引发的异常（我喜欢），因此在扩展类中，您可以处理异常处理程序中的错误。如果你的扩展PDO类中有一个名为getAssoc的方法，那么它将如下所示：

/// Get an associative array of results for the sql.
public function getAssoc($sql, $params=array())
{
   try
   {
      $stmt = $this->prepare($sql);
      $params = is_array($params) ? $params : array($params);
      $stmt->execute($params);

      return $stmt->fetchAll(PDO::FETCH_ASSOC);
   }
   catch (Exception $e)
   {
      // Echo the error or Re-throw it to catch it higher up where you have more
      // information on where it occurred in your program.
      // e.g echo 'Error: ' . $e->getMessage(); 

      throw new Exception(
            __METHOD__ . 'Exception Raised for sql: ' . var_export($sql, true) .
            ' Params: ' . var_export($params, true) .
            ' Error_Info: ' . var_export($this->errorInfo(), true),
            0,
            $e);
   }
}

扩展PDO类

2 个答案: