Concept of singleton pattern
The singleton pattern refers to a design pattern in which a class has only one object instance in the entire application.
Characteristics of the singleton pattern
A class has only one instance in the entire application
The class must create this instance by itself
You must provide this instance to the entire system by yourself
The reason for using the singleton mode in PHP
Most of my operations in PHP involve dealing with various databases, including mysql, redis, Memcache and other relational and non-relational databases, so there will be a large number of operations to connect to the database in an application. If the singleton mode is not used, new operations will be required every time, but each new will consume a lot of memory resources and system resources, and every time a database connection is opened and closed, it is a great test and waste of the database.
Need a static member variable that holds the only instance of the class (usually $instance is a private variable)
Constructors and clone functions must be declared private , in order to prevent the new class of external programs from losing the meaning of the singleton mode
A public static method must be provided to access this instance, thereby returning a reference to the only instance
//设计模式 //单例模式 都是使用同一个对象 //class Ren //{ // public $name; // private static $dx; //存储对象 // // private function __construct() // { // // } // // public static function DuiXiang() // { // if(empty(self::$dx)) // { // self:;$dx=new Ren(); // } // return self::$dx; // } //} // //$r= Ren::DuiXiang(); //把构造函数变为私有 //做了一个方法来间接造对象 //在该方法里面加限制
Factory class
refers to a class that contains a method specifically used to create other objects. The factory class is crucial in the practice of polymorphic programming, which allows dynamic replacement of classes. , modifying the configuration usually makes the application more flexible, and it is important for advanced PHP developers to be proficient in the factory mode.
The factory pattern is usually used to return different classes that conform to similar interfaces. A common use of factories is to create polymorphic providers, allowing us to decide which ones should be instantiated based on application logic or configuration settings. A class, for example, can be extended using such a provider to use the new extended name without the need to refactor other parts of the application.
Usually, the factory pattern has a key construct, which is a static method named Factory according to the general principle. However, this is just a principle. The factory method can be named arbitrarily. This static method can also accept parameters of any data. It must be Return an object.
class YunSuan { public $a; public $b; function Suan() { echo "对两个数进行运算"; }
class gongchang { //功能 : 给一个参数,返回一个对象 static function chanpin($name) { switch($name) { case "'+": return new jia(); break; case "-"; return new jian(); break; } } } $a=gongchang::chanpin("+");
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PHP remains important in modern web development, especially in content management and e-commerce platforms. 1) PHP has a rich ecosystem and strong framework support, such as Laravel and Symfony. 2) Performance optimization can be achieved through OPcache and Nginx. 3) PHP8.0 introduces JIT compiler to improve performance. 4) Cloud-native applications are deployed through Docker and Kubernetes to improve flexibility and scalability.

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.

PHP and Python each have their own advantages and are suitable for different scenarios. 1.PHP is suitable for web development and provides built-in web servers and rich function libraries. 2. Python is suitable for data science and machine learning, with concise syntax and a powerful standard library. When choosing, it should be decided based on project requirements.

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

The reasons why PHP is the preferred technology stack for many websites include its ease of use, strong community support, and widespread use. 1) Easy to learn and use, suitable for beginners. 2) Have a huge developer community and rich resources. 3) Widely used in WordPress, Drupal and other platforms. 4) Integrate tightly with web servers to simplify development deployment.

PHP remains a powerful and widely used tool in modern programming, especially in the field of web development. 1) PHP is easy to use and seamlessly integrated with databases, and is the first choice for many developers. 2) It supports dynamic content generation and object-oriented programming, suitable for quickly creating and maintaining websites. 3) PHP's performance can be improved by caching and optimizing database queries, and its extensive community and rich ecosystem make it still important in today's technology stack.

In PHP, weak references are implemented through the WeakReference class and will not prevent the garbage collector from reclaiming objects. Weak references are suitable for scenarios such as caching systems and event listeners. It should be noted that it cannot guarantee the survival of objects and that garbage collection may be delayed.

The \_\_invoke method allows objects to be called like functions. 1. Define the \_\_invoke method so that the object can be called. 2. When using the $obj(...) syntax, PHP will execute the \_\_invoke method. 3. Suitable for scenarios such as logging and calculator, improving code flexibility and readability.


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