扩展PDO类 [英] extending PDO class
问题描述
下面是到目前为止我得到的数据库连接类,但是我将通过扩展PDO类本身来改进它,
Below is the db connection class I came out with so far, but I am going to improve it by extending the PDO class itself,
<?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()
{
$this->connection = null;
}
}
?>
扩展类
class database extends PDO
{
#make a connection
public function __construct($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式,
This is how I instantiate the class,
# 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类时出现错误,
But I have errors when I call this extended pdo class,
警告:PDO :: __ construct()预期 参数4为数组,给定字符串 在C:\ wamp \ www \ xx \ class_database.php中 在第XX行
Warning: PDO::__construct() expects parameter 4 to be array, string given in C:\wamp\www\xx\class_database.php on line xx
致命错误:调用成员函数 setAttribute()在非对象中 C:\ wamp \ www \ xx \ class_database.php在 xx行
Fatal error: Call to a member function setAttribute() on a non-object in C:\wamp\www\xx\class_database.php on line xx
我已经在网上进行了一些研究,发现了扩展pdo的基本结构,但我不理解...
I have done some research online, I found this basic structure of extending pdo but I dont understand it...
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);
}
}
$ds
n变量的作用是什么?如何将$hostname
变量传递给扩展的pdo类?
What is $ds
n variable for? How can I pass my $hostname
variable into extended pdo class?
另一个问题: 如何制作扩展pdo类中显示错误的方法? 如何在扩展的pdo类中关闭连接?
Another questions: How can I make a method for displaying error in the extended pdo class? How can I close the connection in the extended pdo class?
从mysqli迁移到pdo是如此困难!
It is so difficult to move from mysqli to pdo!
谢谢.
推荐答案
$ dsn是数据源名称.它为您处理您的主机名.您可以这样使用它:
$dsn is data source name. It handles your hostname for you. You use it like this:
$dsn = 'mysql:dbname=YOUR_DB_NAME;host=YOUR_HOSTNAME'
使用$this->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
行,您设置了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.如果您在扩展的PDO类中有一个名为getAssoc的方法,则它将看起来像这样:
With the line $this->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
You have set exceptions to be raised when errors occur (which I like), so in your extended class you can handle errors in exception handlers. If you had a method called getAssoc in your extended PDO class then it would look like this:
/// Get an associative array of results for the sql.
public function getAssoc($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);
}
}
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