But we know that Object-oriented has three main features: inheritance, polymorphism, and encapsulation.
1. Inheritance
We continue with the example in the previous section, in PHP, inheritance and Java are the same, using the extends keyword.
Copy Code code as follows:
class people
{
Private $name;
Public Function GetName ()
{
return $this->name;
}
Public Function SetName ($name)
{
$this->name= $name;
}
}
Class Student extends people
{
Private $grade;
Public Function SayHello ()
{
Echo ("Good morning,". Parent::getname ());
}
}
Here we need the main and we have access to the parent class in C # with base, in Java with Super, but in PHP we use the parent keyword.
If we want to access our own methods, we can use this or self.
Copy Code code as follows:
Class Student extends people
{
Public Function GetName ()
{
return "Kym";
}
Private $grade;
Public Function SayHello ()
{
Echo ("Good morning,". Self::getname ());
Echo ("Good morning,". $this->getname ());
}
}
2. Abstract class
When it comes to inheritance, you have to say abstract classes.
Copy Code code as follows:
<?php
Abstract class people
{
Private $name;
Public Function GetName ()
{
return $this->name;
}
Public Function SetName ($name)
{
$this->name= $name;
}
Abstract function SayHello ();
}
Class Student extends people
{
Public Function SayHello ()
{
Echo ("Good morning,". Parent::getname ());
}
}
$s =new Student ();
$s->setname ("Kym");
$s->sayhello ();
?>
3. Interface
Next is the interface:
Copy Code code as follows:
<?php
Abstract class people
{
Private $name;
Public Function GetName ()
{
return $this->name;
}
Public Function SetName ($name)
{
$this->name= $name;
}
Abstract function SayHello ();
}
Interface Irun
{
function Run ();
}
Class Student extends people implements Irun
{
Public Function SayHello ()
{
Echo ("Good morning,". Parent::getname ());
}
Public Function Run ()
{
Echo ("Two legs Running");
}
}
$s =new Student ();
$s->setname ("Kym");
$s->sayhello ();
$s->run ();
?>
There's nothing to talk about, exactly like Java.
4. Construction Method
Always forget to say that the construction method, in fact, is a piece of the same code:
Copy Code code as follows:
<?php
Class Person
{
Private $name;
Private $age;
Public Function person ($name, $age)
{
$this->name= $name;
$this->age= $age;
}
Public Function SayHello ()
{
Echo ("Hello,my name is". $this->name. ". I ' m ' $this->age);
}
}
$p =new person ("Kym", 22);
$p->sayhello ();
?>
We may often encounter a kind of abnormal type in the interview, that is, the relationship between several classes, and then the constructor and what the transfer to. However, this is not the case in PHP, because the constructor chain is not supported in PHP, which means that when you initialize a subclass, he does not automatically invoke the constructor method of the parent class.
Copy Code code as follows:
<?php
Class Person
{
Private $name;
Private $age;
Public Function person ($name, $age)
{
$this->name= $name;
$this->age= $age;
}
Public Function SayHello ()
{
Echo ("Hello,my name is". $this->name. ". I ' m ' $this->age);
}
}
Class Student extends Person
{
Private $score;
Public Function Student ($name, $age, $score)
{
$this->person ($name, $age);
$this->score= $score;
}
Public function introduce ()
{
Parent::sayhello ();
Echo (". In this exam,i got ". $this->score);
}
}
$s =new Student ("Kym", 22,120);
$s->introduce ();
?>
5. Destructor
Destructors are different from C # and C + +, in PHP, the name of the destructor is __destructor ().
Copy Code code as follows:
Class Student extends Person
{
Private $score;
Public Function Student ($name, $age, $score)
{
$this->person ($name, $age);
$this->score= $score;
}
Public function introduce ()
{
Parent::sayhello ();
Echo (". In this exam,i got ". $this->score);
}
function __destruct ()
{
Echo ("I'm going to be unloaded");
}
}
6. polymorphism
Because of the existence of default parameters, as well as the weak type of PHP, the compile-time polymorphism (i.e. polymorphism due to the number of parameters and different types) is not possible, but Run-time polymorphism is mentioned above. Don't repeat it.
