PHP encapsulation, inheritance, polymorphism

object-oriented three main features : encapsulation, inheritance, polymorphism.

Packaging

Encapsulate classes to make the class more secure so that some member variables cannot be accessed directly by the outside world.

Method:

1. Change the member variable to private.
2. Make a member method in the class to access it indirectly.
3. Add restrictions to this method
4. Each member variable is encapsulated in the standard case.

classren{ Public $name;  Public $sex;  Public $birthday; Private $age; Public functionSetage ($age){        if($age>=18 &&$age<=50){        $this->age =$age;} }     Public functionGetage () {return $this-Age ; }    }        $r=NewRen (); $r->name = "Zhang San"; $r->setage (20); Var_dump($r);

Inherited
Concept: Subclasses can inherit everything from the parent class. The parent class plays a guiding role.
Features: Single inheritance

Keyword: extends

class ren{    public$name;      Public $sex ;      Public function say () {        echo "person in Speech";        }    } class extends ren{    }$cnew China (); $c->say ();

Overriding: Subclasses can override functions of the parent class. Override

Overloading: One method multiple functions, because the number of parameters is different. Method name is the same, the number of parameters is different. Also called compilation polymorphism.

polymorphism: When a parent class reference points to a subclass instance, because the child class overrides the parent class method, the method is called polymorphic when it is called. Also called Run polymorphic.

PHP encapsulation, inheritance, polymorphism