How to call methods of other classes in PHP

PHP is a widely used open source scripting language that is often used for web development and dynamic web page generation. In PHP, we often need to call methods of other classes, which is a common operation. Below, we will introduce how to call methods of other classes in PHP.

1. Use object instantiation

In PHP, if we need to call methods of other classes, we need to instantiate the object of that class first. By instantiating an object of this class, we can access the methods and properties under the object. The code example is as follows:

class Person{
      public function say(){
            echo "hello";
        }
}
//实例化Person
$person = new Person();
//调用Person类中的say()方法
$person->say();

In this example, we instantiate an object of the Person class through the new Person() statement, and later pass $person-> say() to call the say() method in the object.

2. Use static methods or attributes

In PHP, we can also use static methods or attributes to call methods of other classes. Unlike using object instantiation, in static methods or properties, we do not need to instantiate the class object and can directly access the method or property through the class name. The code example is as follows:

class Math{
       //定义一个静态方法multi()
       public static function multi($num1, $num2){
            return $num1 * $num2;
        }
}
//调用静态方法Math::multi()
echo Math::multi(2, 3);

In this example, we call the static method in the Math class by Math::multi(2,3)multi(), and directly print the return value of this method.

3. Using namespaces

In PHP, if we need to call methods in other classes, we can also use namespaces. By giving classes a namespace, we can effectively organize the code in a PHP application. Through namespaces, we can effectively distinguish different classes and functions. The code example is as follows:

namespace MyApp;
class User{
      public function say(){
            echo "MyApp";
       }
}
//通过命名空间，实例化User类
$user = new MyApp\User();
//调用User类中的say()方法
$user->say();

In this example, we use the namespace MyApp statement before the User class to identify that the User class belongs to the MyApp namespace. By instantiating the User class under the MyApp namespace, we can call the say() method in this class.

4. Call parent class methods through inheritance

In PHP, if a class inherits another class, then the subclass can call the method in the parent class. By using the parent keyword, we can call methods in the parent class in the child class. The code example is as follows:

class A{
      public function say(){
            echo "hello";
      }
}
class B extends A{
      public function demo(){
            parent::say();
      }
}
//实例化子类B
$obj = new B();
//调用子类B中的demo()方法
$obj->demo();

In this example, class B inherits from class A, and demo()# in subclass B ##The method calls the say() method in the parent class A by using parent::say().

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