PHP `self` vs. `$this`: When to Use Each?

When to Use 'Self' and '$This' in PHP

In PHP, understanding the distinction between 'self' and '$this' is crucial. 'Self' refers to the current class, while '$this' refers to the current object.

When to Use 'Self':

• Accessing static members (variables or methods):

  class MyClass {
      static $static_member = 10;
  }
  echo MyClass::$static_member; // Output: 10

• Calling parent class methods:

  class ChildClass extends ParentClass {
      public function myMethod() {
          self::parentMethod(); // Calls the parent class method
      }
  }

When to Use '$This':

• Accessing non-static members:

  class MyClass {
      private $instance_member = 20;
  }
  $obj = new MyClass();
  echo $obj->instance_member; // Output: 20

• Calling instance methods:

  class MyClass {
      public function myMethod() {
          echo $this->instance_member; // Accesses the instance member
      }
  }

• Polymorphism: Calling instance methods from derived classes:

  class BaseClass {
      public function myMethod() {
          echo 'BaseClass::myMethod()';
      }
  }
  class DerivedClass extends BaseClass {
      override public function myMethod() {
          echo 'DerivedClass::myMethod()';
      }
  }
  $baseObj = new BaseClass();
  $derivedObj = new DerivedClass();
  $baseObj->myMethod(); // Output: 'BaseClass::myMethod()'
  $derivedObj->myMethod(); // Output: 'DerivedClass::myMethod()'

• Suppressing polymorphism: Calling parent class methods using 'self' in derived classes:

  class BaseClass {
      public function myMethod() {
          echo 'BaseClass::myMethod()';
      }
  }
  class DerivedClass extends BaseClass {
      override public function myMethod() {
          parent::myMethod(); // Calls the BaseClass's myMethod() using self::
      }
  }
  $derivedObj = new DerivedClass();
  $derivedObj->myMethod(); // Output: 'BaseClass::myMethod()'

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