What are the design patterns in PHP?

In the process of developing web applications, using design patterns can improve the readability, maintainability and scalability of the code. PHP is a commonly used Web programming language that also supports the use of various design patterns. This article will introduce commonly used PHP design patterns.

1. Singleton mode (Singleton)
   The singleton mode is used to ensure that a class has only one instance and provides a global access point to access the instance. In PHP, you can use a static property to store the current instance, ensuring that only one instance exists.
2. Factory Pattern (Factory)
   Factory pattern is used to separate the creation and use of objects, creating objects through factory classes instead of directly instantiating them in the code. In PHP, you can use static methods to create objects, and the object class to be created is determined based on the parameters passed.
3. Abstract Factory Pattern (Abstract Factory)
   The Abstract Factory pattern is used to abstract the factory class so that a family of related objects can be created. In PHP, you can define an abstract factory class and a set of factory classes, each factory class is responsible for creating a set of related objects.
4. Strategy Mode (Strategy)
   The strategy mode is used to separate the implementation of the algorithm from the use of the algorithm, and achieve the same function through different algorithms. In PHP, you can define a strategy interface and a set of strategy implementation classes, and implement different algorithms by changing the strategy implementation classes.
5. Observer Pattern (Observer)
   The Observer pattern is used in a one-to-many dependency relationship to notify all objects that depend on it when the state of an object changes. In PHP, the observer pattern can be implemented using the SplSubject and SplObserver interfaces.
6. Adapter pattern (Adapter)
   The adapter pattern is used to convert the interface of a class into another interface to meet the needs of the client. In PHP, you can use the adapter pattern to convert incompatible classes into usable classes, and the adapter class implements the conversion.
7. Decorator pattern (Decorator)
   The decorator pattern is used to dynamically add new behaviors to objects. It is a more flexible design solution for classes that need to extend functionality. In PHP, you can use the decorator pattern to add new behaviors to existing objects without modifying the code of existing classes.
8. Iterator pattern (Iterator)
   The iterator pattern is used to traverse the elements in the aggregate object, separating the traversal process and the data structure, so that the aggregate object and the traversal algorithm can change independently. In PHP, the Iterator pattern can be implemented using the Iterator interface and Iterator class.
9. Bridge mode (Bridge)
   The bridge mode is used to decouple the abstract part and the implementation part so that they can change independently. In PHP, you can use the bridge mode to separate the abstract part and the implementation part and develop them separately. For example, the bridge pattern can be implemented by having the abstract part as an interface and the implementation part as a class.
10. Builder Pattern (Builder)
    Builder pattern is used to build a complex object step by step, separating the construction process from the presentation process, so that the same construction process can create different presentation forms. In PHP, you can use the builder pattern to break down the complex object construction process into multiple simple steps, each step is implemented by a builder class.

Summary:
This article introduces 10 commonly used design patterns in PHP, including singleton pattern, factory pattern, abstract factory pattern, strategy pattern, observer pattern, adapter pattern, and decorator pattern, iterator pattern, bridge pattern and builder pattern, each design pattern has corresponding application scenarios and implementation methods. Developers can choose appropriate design patterns to optimize their code based on specific needs.

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