我们应该将pdo的function __construct设置为private还是public？如果我将其设置为public？
这是我的db类，
class pdo_connection
{
public $connection; // handle of the db connexion
public function __construct($dsn = 'mysql:host=localhost;dbname=xxx_2013',$username = 'root',$password = 'xxx')
{
$this->dsn = $dsn;
$this->username = $username;
$this->password = $password;
$this->connection();
}
private function connection()
{
try
{
$this->connection = new PDO($this->dsn, $this->username, $this->password, array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8"));
$this->connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
catch (PDOException $e)
{
# call the get_error function
$this->get_error($e);
}
// return $this->connection;
}
...
}
修改
class database extends common
{
/**
* Set the class property.
*/
protected $connection = null;
protected $dsn,$username,$password;
/**
* Set the class contructor.
* @reference: http://us.php.net/manual/en/language.oop5.magic.php#object.sleep
*/
public function __construct($dsn,$username,$password)
{
$this->dsn = $dsn;
$this->username = $username;
$this->password = $password;
//$this->connect();
}
/**
* make the pdo connection.
* @return object $connection
*/
public function connect()
{
try
{
# MySQL with PDO_MYSQL
# To deal with special characters and Chinese character, add charset=UTF-8 in $dsn and array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8").
$this->connection = new PDO($this->dsn, $this->username, $this->password, array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8"));
$this->connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
catch (PDOException $e)
{
# call the get_error function
$this->get_error($e);
}
}
/**
* get the number of rows in a result as a value string.
* @param string $query
* @param array $params
* @return number
*/
public function num_rows($query, $params = array())
{
try
{
# create a prepared statement
$stmt = $this->connection->prepare($query);
# if $params is not an array, let's make it array with one value of former $params
if (!is_array($params)) $params = array($params);
# execute the query
$stmt->execute($params);
# return the result
return $stmt->rowCount();
}
catch (PDOException $e)
{
# call the get_error function
$this->get_error($e);
}
}
/**
* fetch a single row of result as an array ( = one dimensional array).
* @param string $query
* @param array $params
* @param boolean $array_to_object
* @return object/ array
*/
public function fetch_assoc($query, $params = array(), $array_to_object = true)
{
try
{
# prepare the query
$stmt = $this->connection->prepare($query);
# if $params is not an array, let's make it array with one value of former $params
if (!is_array($params)) $params = array($params);
# the line
//$params = is_array($params) ? $params : array($params);
# is simply checking if the $params variable is an array, and if so, it creates an array with the original $params value as its only element, and assigns the array to $params.
# This would allow you to provide a single variable to the query method, or an array of variables if the query has multiple placeholders.
# The reason it doesn't use bindParam is because the values are being passed to the execute() method. With PDO you have multiple methods available for binding data to placeholders:
# bindParam
# bindValue
# execute($values)
# The big advantage for the bindParam method is if you are looping over an array of data, you can call bindParam once, to bind the placeholder to a specific variable name (even if that variable isn't defined yet) and it will get the current value of the specified variable each time the statement is executed.
# execute the query
$stmt->execute($params);
# return the result
if($array_to_object) return parent::array_to_object($stmt->fetch());
else return $stmt->fetch();
}
catch (PDOException $e)
{
# call the get_error function.
$this->get_error($e);
}
/*
or,
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);
}
*/
}
/**
* fetch a multiple rows of result as a nested array ( = multi-dimensional array).
* @param string $query
* @param array $params
* @param boolean $array_to_object
* @return object/ array
*/
public function fetch_all($query, $params = array(), $array_to_object = true)
{
try
{
# prepare the query
$stmt = $this->connection->prepare($query);
# if $params is not an array, let's make it array with one value of former $params
if (!is_array($params)) $params = array($params);
# when passing an array of params to execute for a PDO statement, all values are treated as PDO::PARAM_STR.
# use bindParam to tell PDO that you're using INTs
# wrap the bindParam function in a foreach that scan your parameters array
# it's $key + 1 because arrays in PHP are zero-indexed, but bindParam wants the 1st parameter to be 1, not 0 (and so on).
/*
foreach($params as $key => $param)
{
if(is_int($param))
{
$stmt->bindParam($key + 1, $param, PDO::PARAM_INT);
}
else
{
$stmt->bindParam($key + 1, $param, PDO::PARAM_STR);
}
}
# execute the query
$stmt->execute();
*/
# execute the query
$stmt->execute($params);
# return the result
if($array_to_object) return parent::array_to_object($stmt->fetchAll(PDO::FETCH_ASSOC));
else return $stmt->fetchAll(PDO::FETCH_ASSOC);
}
catch (PDOException $e)
{
# call the get_error function
$this->get_error($e);
}
}
/**
* return the current row of a result set as an object.
* @param string $query
* @param array $params
* @return object
*/
public function fetch_object($query, $params = array())
{
try
{
# prepare the query
$stmt = $this->connection->prepare($query);
# if $params is not an array, let's make it array with one value of former $params
if (!is_array($params)) $params = array($params);
# execute the query
$stmt->execute($params);
# return the result
return $stmt->fetchObject();
//return $stmt->fetch(PDO::FETCH_OBJ);
}
catch (PDOException $e)
{
# call the get_error function
$this->get_error($e);
}
}
/**
* insert or update data.
* @param string $query
* @param array $params
* @return boolean - true.
*/
public function run_query($query, $params = array())
{
try
{
$stmt = $this->connection->prepare($query);
$params = is_array($params) ? $params : array($params);
$stmt->execute($params);
return true;
}
catch (PDOException $e)
{
# call the get_error function
$this->get_error($e);
}
}
/**
* with __sleep, you return an array of properties you want to serialize. the point is to be able to exclude properties that are not serializable. eg: your connection property.
* @return array
*/
public function __sleep()
{
return array('dsn', 'username', 'password');
}
/**
* the intended use of __wakeup() is to reestablish any database connections that may have been lost during serialization and perform other reinitialization tasks.
*/
public function __wakeup()
{
$this->connect();
//$this->connection = new PDO($this->dsn, $this->username, $this->password, array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8"));
//$this->connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
/**
* display error.
* @return string
*/
public function get_error($e)
{
$this->connection = null;
die($e->getMessage());
}
/**
* close the database connection when object is destroyed.
*/
public function __destruct()
{
# set the handler to NULL closes the connection propperly
$this->connection = null;
}
}
用法：
$database = new database(DSN,DB_USER,DB_PASS);
$connection = $database->connect();
var_dump($connection);
结果，
null
它应该是，
object(database)[1]
protected 'connection' =>
object(PDO)[2]
protected 'dsn' => string 'mysql:host=localhost;dbname=xxx_2013' (length=42)
protected 'username' => string 'xxx' (length=4)
protected 'password' => string 'xxx' (length=5)
答案 0 :(得分：7)
没有。你在考虑这个错误。您的公共方法是您向其他使用您的类的开发人员提供的API。
在编写课程结束时，想象一下，您正在将文档交给另一位开发人员。您将列出其他开发人员可以使用的“端点”。目前这些是：
__construct() connection() 显然，您希望connection()更像connect()，因为对于查看代码的其他开发人员而言，它更有意义。即使makeConnection()更好。
单身人士很不可能
将构造函数设置为private通常是出于以下原因：单例。你想要避免全球状态，单身等等 - 他们是不好的做法，让测试变得更加艰难。
在对象位于共享内存中的语言中，可以使用单例来降低内存使用率。您可以从全局共享的应用程序内存中引用现有实例，而不是创建两个对象。在PHP中没有这样的应用程序内存。在一个请求中创建的Singleton仅适用于该请求。在另一个同时完成的请求中创建的Singleton仍然是一个完全不同的实例。因此，Singleton的两个主要目的之一在这里不适用。
阅读 this post ，深入了解为什么单身人士只是愚蠢。如果您不想要多个连接实例，不创建一个。如果你不能创建一个，那么你需要重新考虑你的架构（这不应该太糟糕，因为处理数据库的东西通常是在你正在做的任何事情的早期阶段。）
最后，您的构造函数需要 public 。为什么？因此，使用它的开发人员（想象自己是另一个开发人员）可以将其用于预期目的。
额外说明：
您的用户名/密码不应该硬编码到类构造函数中，您应该在创建对象时传递它们。
不要从构造函数中调用$this->connection()。如果你这样做的话，你可以把它全部推到那里。相反，请致电：
$db = new pdo_connection($username, $password, $etc);
$db->connection();
这意味着您可以将对象传递到任何您喜欢的位置，但在运行connection()方法时只使用资源（创建连接）。