Php 使用继承时对象声明中出错
我用了三节课。两个类扩展了第三个类db。但问题是,当我声明这些类的对象时,第二个对象被创建为第一个对象的克隆。提前感谢您的帮助Php 使用继承时对象声明中出错,php,oop,class,constructor,Php,Oop,Class,Constructor,我用了三节课。两个类扩展了第三个类db。但问题是,当我声明这些类的对象时,第二个对象被创建为第一个对象的克隆。提前感谢您的帮助 class db extends PDO { public function __construct() { echo "DB constructor called\n"; .. } class Admin extends db { private $uid,
class db extends PDO {
public function __construct() {
echo "DB constructor called\n";
..
}
class Admin extends db {
private $uid, $username, $password, $level, $name, $email;
public function __construct() {
echo "Admin constructor called\n";
parent::__construct();
}
class Movie extends db {
private $mid, $title, $slug;
public function __construct() {
echo "Movie constructor called\n";
parent::__construct();
}
输出为
Admin constructor called
DB constructor called
Movie constructor called
DB constructor called
object(Admin)#1 (11) {
["uid":"Admin":private]=>
NULL
["username":"Admin":private]=>
NULL
["password":"Admin":private]=>
NULL
["level":"Admin":private]=>
NULL
["name":"Admin":private]=>
NULL
["email":"Admin":private]=>
NULL
["error":"db":private]=>
NULL
["sql":"db":private]=>
NULL
["bind":"db":private]=>
NULL
["errorCallbackFunction":"db":private]=>
NULL
["errorMsgFormat":"db":private]=>
NULL
}
object(Admin)#2 (11) {
["uid":"Admin":private]=>
NULL
["username":"Admin":private]=>
NULL
["password":"Admin":private]=>
NULL
["level":"Admin":private]=>
NULL
["name":"Admin":private]=>
NULL
["email":"Admin":private]=>
NULL
["error":"db":private]=>
NULL
["sql":"db":private]=>
NULL
["bind":"db":private]=>
NULL
["errorCallbackFunction":"db":private]=>
NULL
["errorMsgFormat":"db":private]=>
NULL
}
修改代码,请对此进行分析。当父项::u构造($dsn,DB_用户,DB_密码,$options);在db类中,问题将消失
<?php
/** The Database Driver */
define('DB_DRIVER', 'mysql');
/** The name of the database */
define('DB_NAME', 'sample');
/** MySQL database username */
define('DB_USER', 'root');
/** MySQL database password */
define('DB_PASSWORD', 'root');
/** MySQL hostname */
define('DB_HOST', 'localhost');
class db extends PDO
{
public function __construct()
{
echo "DB constructor called\n";
$options = array(
PDO::ATTR_PERSISTENT => true,
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION
);
$dsn = DB_DRIVER . ":host=" . DB_HOST . ";dbname=" . DB_NAME;
parent::__construct($dsn, DB_USER, DB_PASSWORD, $options);
}
}
class Admin extends db
{
private $uid, $username, $password, $level, $name, $email;
public function __construct()
{
echo "Admin constructor called\n";
parent::__construct();
}
}
class Movie extends db
{
private $mid, $title, $slug;
public function __construct()
{
echo "Movie constructor called\n";
parent::__construct();
}
}
$adminObj = new Admin();
$movieObj = new Movie();
var_dump($adminObj);
var_dump($movieObj);
?>
它们不是克隆。它们都是从db类继承的,您还没有对它们做任何更改。它们不是克隆—它们完全相同。如果要防止2个PDO实例,请使用我看不出有任何问题—输出完全符合预期。因此,在您包含的文件中的其他地方,它一定是一个错误。以下是独立测试代码:
<?php
class db extends PDO
{
public function __construct()
{
echo "DB constructor called\n";
}
}
class Admin extends db
{
private $uid, $username, $password, $level, $name, $email;
public function __construct()
{
echo "Admin constructor called\n";
parent::__construct();
}
}
class Movie extends db
{
private $mid, $title, $slug;
public function __construct()
{
echo "Movie constructor called\n";
parent::__construct();
}
}
$adminObj = new Admin();
$movieObj = new Movie();
var_dump($adminObj);
var_dump($movieObj);
所以请检查您的实际代码。可能(只是可能)你把错误的文件包括进去了。。或者第二个类在另一个地方被声明(您可能编辑了错误的文件)
编辑:
亚历克斯,谢谢你提供更多信息。我在您更新的代码中发现了问题:
PDO::ATTR_PERSISTENT=>true
,--将true
更改为false
,并看到了区别:)您能用较小的系统重新创建此问题吗。我很想做这件事,但最近我没有多少空闲时间。如果你能在一个较小的系统中观察到这个问题,那么它肯定是一个bug。由于完整的代码不在这里,我不能确定。@cem kalyoncu感谢您对我的问题表现出兴趣。我将在一个较小的系统中重新创建该情况,并在此处进行更新。请稍候。@Cem Kalyoncu我已将具有相同问题的较小代码放置在。请检查。使用依赖注入模式或服务定位器模式会更好。我已经在问题中添加了关于测试代码的修改代码。请检查。@Alex:在更新的代码中发现问题:PDO::ATTR_PERSISTENT=>true,
--将其更改为false
,并查看差异:)。另外--我相信您自己会找到关于此属性的文档。
<?php
class db extends PDO
{
public function __construct()
{
echo "DB constructor called\n";
}
}
class Admin extends db
{
private $uid, $username, $password, $level, $name, $email;
public function __construct()
{
echo "Admin constructor called\n";
parent::__construct();
}
}
class Movie extends db
{
private $mid, $title, $slug;
public function __construct()
{
echo "Movie constructor called\n";
parent::__construct();
}
}
$adminObj = new Admin();
$movieObj = new Movie();
var_dump($adminObj);
var_dump($movieObj);
Admin constructor called
DB constructor called
Movie constructor called
DB constructor called
object(Admin)#1 (6) {
["uid":"Admin":private]=>
NULL
["username":"Admin":private]=>
NULL
["password":"Admin":private]=>
NULL
["level":"Admin":private]=>
NULL
["name":"Admin":private]=>
NULL
["email":"Admin":private]=>
NULL
}
object(Movie)#2 (3) {
["mid":"Movie":private]=>
NULL
["title":"Movie":private]=>
NULL
["slug":"Movie":private]=>
NULL
}