Common methods and techniques for PHP classes to use methods of other classes

In PHP programming, we often use classes to organize and manage code. In fact, a class can use the methods and properties of other classes, making the code more modular and flexible. This article will introduce common methods and techniques for PHP classes to use other class methods.

1. Inheritance

Inheritance is a classic feature in object-oriented programming. It can help us avoid code duplication and improve code maintainability. When a class needs to use the methods of another class, we can achieve this need through inheritance.

The specific implementation method is to use the extends keyword in the subclass to inherit the parent class, as shown below:

class ParentClass {
    public function foo(){
        // some codes here
    }
}

class ChildClass extends ParentClass {
    public function bar(){
        $this->foo(); // call parent method
    }
}

By inheriting the parent class, the subclass can inherit all the methods and methods of the parent class Properties, and can call methods of the parent class in the subclass.

In short, inheritance is a very common and practical feature, which can greatly improve the flexibility and reusability of code.

2. Implementing interfaces

Another common method is to use interfaces to define relationships and specifications between classes. When a class needs to use some methods of another class, we can let the class implement the appropriate interface.

In PHP, an interface is a set of abstract methods that defines what behaviors and capabilities a class should have. When a class implements an interface, it means that the class needs to implement all the abstract methods in the interface.

The specific implementation method is to use the implements keyword in the class to implement the interface, as shown below:

interface MyInterface {
    public function foo();
}

class MyClass implements MyInterface {
    public function foo(){
        // some codes here
    }
}

$obj = new MyClass();
$obj->foo(); // call implemented method

By implementing the interface, the class can obtain some defined methods and can be used in the class use these methods.

In short, interface is a very useful feature, which can standardize the relationship and behavior between classes to a certain extent, and can improve the modularity of the code.

3. Using Dependency Injection

Another more flexible method is to use dependency injection. It is an object-oriented programming practice primarily used to resolve dependencies between classes.

The specific implementation method is to inject instances of other classes through parameters in the constructor of the class, as shown below:

class DependencyClass {
    public function foo(){
        // some codes here
    }
}

class MainClass {
    private $dep;

    public function __construct(DependencyClass $dep) {
        $this->dep = $dep;
    }

    public function bar() {
        $this->dep->foo(); // call injected class method
    }
}

$dep = new DependencyClass();
$obj = new MainClass($dep);
$obj->bar(); // call injected dependency method

Through dependency injection, the main class can obtain other classes when needed. Instances of classes and methods of these instances can be called in the main class.

In short, dependency injection is a very flexible method that can help us manage the dependencies between classes more clearly, thereby achieving high maintainability and high reusability of the code.

Summary

In this article, we introduced common methods and techniques for PHP classes to use methods of other classes, including inheritance, implementing interfaces, and using dependency injection. Some of these methods are based on static relationships between classes, and some are based on dynamic relationships between classes. They can all help us write more modular and clear code and improve our development efficiency.

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