Php abstract class, interface, trait, final

php-class-abstract_interface_trait_final.php

<?php
echo "ABSTRACT : DECLARE CLASS THE WAY YOU WANT", "\n\n";
abstract class AbstractClass
{
    // Our abstract method only needs to define the required parameters
    abstract protected function prefixName($name);

}

class ConcreteClass extends AbstractClass
{

    // Our subclass can define optional parameters that do not exist in the parent signature
    public function prefixName($name, $separator = ".") {
        if ($name == "Pacman") {
            $prefix = "Mr";
        } elseif ($name == "Pacwoman") {
            $prefix = "Mrs";
        } else {
            $prefix = "";
        }
        return "{$prefix}{$separator} {$name}";
    }

}

$class = new ConcreteClass;
echo $class->prefixName("Pacman"), "\n";
echo $class->prefixName("Pacwoman"), "\n\n";

echo "--------------------------------", "\n";
echo "INTERFACE : SAME AS ABSTRACT BUT PUBLICLY", "\n";
echo "An interface is a special abstract class that can also be thought of as a specification for a model", "\n\n";
// Define the interface
interface User{
    function getDiscount();
    function getUserType();
}
 //VIP user interface implementation
class VipUser implements User{
         // VIP user discount factor
    private $discount = 0.8;
    function getDiscount() {
        return $this->discount;
    }
    function getUserType() {
        Return "VIP user";
    }
}
class Goods {
    var $price = 100;
    var $vc;
    // Define the User interface type parameter, then do not know what user
    
    function run(User $vc){
        $this->vc = $vc;
        $discount = $this->vc->getDiscount();
	    $usertype = $this->vc->getUserType();
        
        Echo $usertype."Commodity Price:".$this->price*$discount;
    }
}

$display = new Goods();
$display ->run(new VipUser); //can be more other user types
echo "\n\n";

echo "--------------------------------", "\n";
echo "TRAIT : ADD METHOD WITHOUT BEING A PARENT", "\n\n";

trait Hello {
    public function sayHello() {
        echo 'Hello ';
    }
}

trait World {
    public function sayWorld() {
        echo 'World';
    }
}

class MyHelloWorld {
    use Hello, World;
    public function sayExclamationMark() {
        echo '!';
    }
}

$o = new MyHelloWorld();
$o->sayHello();
$o->sayWorld();
$o->sayExclamationMark();
# Hello World!
echo "\n\n";

echo "--------------------------------", "\n";
echo "FINAL : METHOD THAT CAN'T BE INHERITED/OVERRIDED", "\n\n";

class BaseClass {
   public function test() {
       echo "BaseClass::test() called\n";
   }
   
   final public function moreTesting() {
       echo "BaseClass::moreTesting() called\n";
   }
}

class ChildClass extends BaseClass {
    // Results in Fatal error: Cannot override final method BaseClass::moreTesting()
    /* 
   public function moreTesting() {
       echo "ChildClass::moreTesting() called\n";
   }
   */
}

final class BaseClass2 {
   public function test() {
       echo "BaseClass::test() called\n";
   }
   
   // No matter whether you declare the method as final or not, it doesn't matter.
   final public function moreTesting() {
       echo "BaseClass::moreTesting() called\n";
   }
}

// Generate Fatal error: Class ChildClass may not inherit from final class (BaseClass)
/*
class ChildClass extends BaseClass2 {
}
 */

// src : https://www.programmersought.com/article/79471399333/