How does php introduce another class in a class?

To introduce another class to a class in php, you can use the value transfer or inheritance method.

Sometimes you need to call methods in another class in one class,

Then another class needs to call the method of the current class. what should I do?

You can directly introduce class objects to call methods of another class.

Example)

Class a {function B ($ obj) {$ obj-> test () ;}} class B {function test () {echo 'test ';}} $ a = new a (); $ B-> B (new B ());

Inheritance method. if the subclass defines the same method, the method of the parent class will be overwritten.

Class B {function _ construct () {} function testb () {echo 'test';} class a extends B {function _ construct () {parent :: testb (); // or like this $ this-> testb () ;}// repeated definitions will overwrite function testb () {echo 123 ;}} $ a = new ();