Learn PHP(6) object-oriented step by step_PHP tutorial

But we know that object-oriented has three major characteristics: inheritance, polymorphism and encapsulation.

1. Inheritance

Let’s continue the example in the previous section. In PHP, inheritance is the same as Java, both using the extends keyword.

Copy code The code is 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, the main thing we need is that we access the parent class using base in C# and super in Java, but in In PHP, we use the parent keyword.

If we want to access our own methods, we can use this or self.

Copy code The code is 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, we have to talk about abstract classes.

Copy code The code is as follows:

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

The next step is the interface:

Copy code The code is as follows:

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("Running on two legs");
}
}
$s=new Student();
$s->SetName("kym");
$s->SayHello();
$s->Run();
?>

There is nothing to say, it is exactly the same as Java.

4. Construction method

I always forgot to mention the construction method, which is actually the same code:

Copy Code The code is as follows:

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 this in interviews A perverted question type is the relationship between several classes, and then the constructors and other things are adjusted back and forth. However, you will not encounter such a situation in PHP, because PHP does not support constructor chains, that is to say, when you initialize a subclass, it will not automatically call the constructor of the parent class.

Copy code The code is as follows:

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

The destructor is different from C# and C++. In PHP, the name of the destructor is __destructor().

Copy code The code is 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 uninstalled");
}
}

6. Polymorphism

Due to the existence of default parameters and the weak type of PHP, compile-time polymorphism (that is, polymorphism caused by different number and types of parameters) cannot be implemented, but run-time polymorphism is Already mentioned above. No more details.

http://www.bkjia.com/PHPjc/321285.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/321285.htmlTechArticleBut we know that object-oriented has three major characteristics: inheritance, polymorphism and encapsulation. 1. Inheritance Let’s continue the example in the previous section. In PHP, inheritance is the same as Java, both using extends...