Backend Development
PHP Tutorial
Detailed explanation of problems encountered in inheritance of PHP singleton mode
Detailed explanation of problems encountered in inheritance of PHP singleton mode
Detailed explanation of PHPSingle case modeInheritanceProblems encountered
<?php
// 单例模式之继承
class Singleton
{
protected static $ins = null;
private final function construct() { }
protected final function clone() { }
// public static function getIns() {
// if(self::$ins === null){
// self::$ins = new self();
// }
// return self::$ins;
// }
public static function getIns() {
if(static::$ins === null){
static::$ins = new static();
}
return static::$ins;
}
}
class Child extends Singleton
{
// protected static $ins = null;
}
/*
输出结果为：
bool(true) object(Singleton)#1 (0) { }
问题：对象 $c1, $c2 竟然都是 Singleton 的实例 ???
解决方法：将 getIns() 方法中关键字 self 替换为 static, 利用后期静态绑定的特性
*/
$c1 = Child::getIns();
$c2 = Child::getIns();
var_dump($c1 === $c2); //true
var_dump($c1);
// ------------------------------------------------------------------------
// 另一个问题
/*
输出结果为：
bool(true) object(Child)#1 (0) { }
问题：对象 $c3 竟然是 Child 的实例, 实际上应该是 Singleton 的实例 ???
原因：因为 $ins 属性是从父类 Singleton 继承过来的, 当第一次调用 Child::getIns() 时, $ins = new Child()
当再次调用 Singleton::getIns() 时, $ins 已经被实例过了, 而且指向 Child 的实例,
所以此时 $c3 变成了 Child 的实例
解决方法：在 Child 类中, 声明自己独有的 $ins 属性
*/
$c3 = Singleton::getIns();
var_dump($c1 === $c3);
var_dump($c3);The getIns() method of late static binding There is another problem:
If the $ins property of Singleton is set to private, the subclass Child must set its own $ins property,
Because static::$ins first looks for the subclass's own $ins attribute, but since the subclass is not declared and the parent class cannot inherit it, Child::getIns() is called at this time
The method will report an error:
Fatal error: Cannot access property Child::$ins in D:\wamp\www\mycode\DesignPattern\Singleton.php on line 27
Solution:
#Set the $ins attribute of the parent class Singleton to protected or set the subclass Child's own $ins Attributes
The above is the detailed content of Detailed explanation of problems encountered in inheritance of PHP singleton mode. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
1668
14
1428
52
1329
25
1273
29
1256
24
PHP: A Key Language for Web Development
Apr 13, 2025 am 12:08 AM
PHP is a scripting language widely used on the server side, especially suitable for web development. 1.PHP can embed HTML, process HTTP requests and responses, and supports a variety of databases. 2.PHP is used to generate dynamic web content, process form data, access databases, etc., with strong community support and open source resources. 3. PHP is an interpreted language, and the execution process includes lexical analysis, grammatical analysis, compilation and execution. 4.PHP can be combined with MySQL for advanced applications such as user registration systems. 5. When debugging PHP, you can use functions such as error_reporting() and var_dump(). 6. Optimize PHP code to use caching mechanisms, optimize database queries and use built-in functions. 7
PHP and Python: Comparing Two Popular Programming Languages
Apr 14, 2025 am 12:13 AM
PHP and Python each have their own advantages, and choose according to project requirements. 1.PHP is suitable for web development, especially for rapid development and maintenance of websites. 2. Python is suitable for data science, machine learning and artificial intelligence, with concise syntax and suitable for beginners.
PHP vs. Python: Understanding the Differences
Apr 11, 2025 am 12:15 AM
PHP and Python each have their own advantages, and the choice should be based on project requirements. 1.PHP is suitable for web development, with simple syntax and high execution efficiency. 2. Python is suitable for data science and machine learning, with concise syntax and rich libraries.
PHP in Action: Real-World Examples and Applications
Apr 14, 2025 am 12:19 AM
PHP is widely used in e-commerce, content management systems and API development. 1) E-commerce: used for shopping cart function and payment processing. 2) Content management system: used for dynamic content generation and user management. 3) API development: used for RESTful API development and API security. Through performance optimization and best practices, the efficiency and maintainability of PHP applications are improved.
Explain the difference between self::, parent::, and static:: in PHP OOP.
Apr 09, 2025 am 12:04 AM
In PHPOOP, self:: refers to the current class, parent:: refers to the parent class, static:: is used for late static binding. 1.self:: is used for static method and constant calls, but does not support late static binding. 2.parent:: is used for subclasses to call parent class methods, and private methods cannot be accessed. 3.static:: supports late static binding, suitable for inheritance and polymorphism, but may affect the readability of the code.
The Enduring Relevance of PHP: Is It Still Alive?
Apr 14, 2025 am 12:12 AM
PHP is still dynamic and still occupies an important position in the field of modern programming. 1) PHP's simplicity and powerful community support make it widely used in web development; 2) Its flexibility and stability make it outstanding in handling web forms, database operations and file processing; 3) PHP is constantly evolving and optimizing, suitable for beginners and experienced developers.
PHP and Python: Different Paradigms Explained
Apr 18, 2025 am 12:26 AM
PHP is mainly procedural programming, but also supports object-oriented programming (OOP); Python supports a variety of paradigms, including OOP, functional and procedural programming. PHP is suitable for web development, and Python is suitable for a variety of applications such as data analysis and machine learning.
PHP vs. Other Languages: A Comparison
Apr 13, 2025 am 12:19 AM
PHP is suitable for web development, especially in rapid development and processing dynamic content, but is not good at data science and enterprise-level applications. Compared with Python, PHP has more advantages in web development, but is not as good as Python in the field of data science; compared with Java, PHP performs worse in enterprise-level applications, but is more flexible in web development; compared with JavaScript, PHP is more concise in back-end development, but is not as good as JavaScript in front-end development.
