why used to interface rather than class in below condition.

Question

i want to show a name.name may be in uppercase or in lowercase this will be depend on which class i will pass.i have to approach one is using class and second is interface which one is better and why ?

1. Solution using Class

   class User{
   
   }
   
   class Iuser extends User{
       private $name;
       function  __construct($name){
           $this->name = $name;
       }
       function getName(){
           return strtoupper($this->name);
       }
   }
   
   class Wuser extends User{
       private $name;
       function  __construct($name){
           $this->name = $name;
       }
       function getName(){
           return strtolower($this->name);
       }
   }
   
   class Name{
     public $u;
     function  __construct(User $u){
         $this->u = $u;
     }
   
     function getName(){
         $name  = $this->u->getName();
         return "Hi My Name is ".$name; 
     }
   }
   
   $name = "Deval Patel";
   $iu = new Iuser($name);
   $wu = new Wuser($name);
   $user = new Name($wu);
   echo $user->getName();
   

2. Solution Using Interface

   interface User{
       public function getName();
   }
   
   class Iuser implements User{
       private $name;
       function  __construct($name){
           $this->name = $name;
       }
       function getName(){
           return strtoupper($this->name);
       }
   }
   
   class Wuser implements User{
       private $name;
       function  __construct($name){
           $this->name = $name;
       }
       function getName(){
           return strtolower($this->name);
       }
   }
   
   class Name{
     public $u;
     function  __construct(User $u){
         $this->u = $u;
     }
   
     function getName(){
         $name  = $this->u->getName();
         return "Hi My Name is ".$name; 
     }
   }
   
   $name = "Deval Patel";
   $iu = new Iuser($name);
   $wu = new Wuser($name);
   $user = new Name($iu);
   echo $user->getName();
   

Answer 1

Using the interface solution the getName() method is defined but not implemented in User interface (not shown in your code), so each class implementing it has to define the behaviour to get the name, whilst using abstract classes you may define the standard way to get the name, and override or overload the method in child classes when necessary.

So for your code, I think the best solution is the abstraction.

Remember to use interfaces when you want to force the developer to code the getName() method, and for abstract classes just to allow the developer to use the parent method getName(), or override/overload if necessary. Interfaces gives you more control and code reutilization.

Review the PHP object interfaces doc and PHP class abstraction doc, it may shed some light on your doubt.