这里有一些注意事项：
- 编写此代码是为了考虑几个遗留问题，例如数据库日志记录和数据库配置管理。
- 我强烈建议您在构建自己的解决方案之前先查看现有的解决方案。很多人在开始时都认为他们不想使用现有的框架或库，因为它们太大了，需要太多的时间来学习等等，但是在成为这些人之一之后，我不能强调我离开我的自定义框架和包装类来移动到框架。我希望搬到Zend，但有很多很好的选择。
哦，我应该指出，这一点说明了如何包装单个函数来处理查询的所有异常处理。我现在几乎不会在其他任何地方编写 try catch 块，因为来自查询的堆栈跟踪为我提供了调试问题和修复问题所需的所有信息。
以下是我当前的 PDO 包装类实现：
class DB extends PDO
{
// Allows implementation of the singleton pattern -- ndg 5/24/2008
private static $instance;
// Public static variables for configuring the DB class for a particular database -- ndg 6/16/2008
public static $error_table;
public static $host_name;
public static $db_name;
public static $username;
public static $password;
public static $driver_options;
public static $db_config_path;
function __construct($dsn="", $username="", $password="", $driver_options=array())
{
if(isset(self::$db_config_path))
{
try
{
if(!require_once self::$db_config_path)
{
throw new error('Failed to require file: ' . self::$db_config_path);
}
}
catch(error $e)
{
$e->emailAdmin();
}
}
elseif(isset($_ENV['DB']))
{
self::$db_config_path = 'config.db.php';
try
{
if(!require_once self::$db_config_path)
{
throw new error('Failed to require file: ' . self::$db_config_path);
}
}
catch(error $e)
{
$e->emailAdmin();
}
}
parent::__construct("mysql:host=" . self::$host_name . ";dbname=" .self::$db_name, self::$username, self::$password, self::$driver_options);
$this->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$this->setAttribute(PDO::ATTR_STATEMENT_CLASS, array('QueryStatement', array($this)));
if(!isset(self::$error_table))
{
self::$error_table = 'errorlog_rtab';
}
}
/**
* Return a DB Connection Object
*
* @return DB
*/
public static function connect()
{
// New PDO Connection to be used in NEW development and MAINTENANCE development
try
{
if(!isset(self::$instance))
{
if(!self::$instance = new DB())
{
throw new error('PDO DB Connection failed with error: ' . self::errorInfo());
}
}
return self::$instance;
}
catch(error $e)
{
$e->printErrMsg();
}
}
/**
* Returns a QueryBuilder object which can be used to build dynamic queries
*
* @return QueryBuilder
*
*/
public function createQuery()
{
return new QueryBuilder();
}
public function executeStatement($statement, $params = null, $FETCH_MODE = null)
{
if($FETCH_MODE == 'scalar')
{
return $this->executeScalar($statement, $params);
}
try {
try {
if(!empty($params))
{
$stmt = $this->prepare($statement);
$stmt->execute($params);
}
else
{
$stmt = $this->query($statement);
}
}
catch(PDOException $pdo_error)
{
throw new error("Failed to execute query:\n" . $statement . "\nUsing Parameters:\n" . print_r($params, true) . "\nWith Error:\n" . $pdo_error->getMessage());
}
}
catch(error $e)
{
$this->logDBError($e);
$e->emailAdmin();
return false;
}
try
{
if($FETCH_MODE == 'all')
{
$tmp = $stmt->fetchAll();
}
elseif($FETCH_MODE == 'column')
{
$arr = $stmt->fetchAll();
foreach($arr as $key => $val)
{
foreach($val as $var => $value)
{
$tmp[] = $value;
}
}
}
elseif($FETCH_MODE == 'row')
{
$tmp = $stmt->fetch();
}
elseif(empty($FETCH_MODE))
{
return true;
}
}
catch(PDOException $pdoError)
{
return true;
}
$stmt->closeCursor();
return $tmp;
}
public function executeScalar($statement, $params = null)
{
$stmt = $this->prepare($statement);
if(!empty($this->bound_params) && empty($params))
{
$params = $this->bound_params;
}
try {
try {
if(!empty($params))
{
$stmt->execute($params);
}
else
{
$stmt = $this->query($statement);
}
}
catch(PDOException $pdo_error)
{
throw new error("Failed to execute query:\n" . $statement . "\nUsing Parameters:\n" . print_r($params, true) . "\nWith Error:\n" . $pdo_error->getMessage());
}
}
catch(error $e)
{
$this->logDBError($e);
$e->emailAdmin();
}
$count = $stmt->fetchColumn();
$stmt->closeCursor();
//echo $count;
return $count;
}
protected function logDBError($e)
{
$error = $e->getErrorReport();
$sql = "
INSERT INTO " . self::$error_table . " (message, time_date)
VALUES (:error, NOW())";
$this->executeStatement($sql, array(':error' => $error));
}
}
class QueryStatement extends PDOStatement
{
public $conn;
protected function __construct()
{
$this->conn = DB::connect();
$this->setFetchMode(PDO::FETCH_ASSOC);
}
public function execute($bound_params = null)
{
return parent::execute($bound_params);
}
}
