Final Keyword

PHP 5 introduces the final keyword, which prevents child classes from overriding a method by prefixing the definition with final. If the class itself is being defined final then it cannot be extended.

Example 19-28. Final methods example


<?php

class BaseClass {

   public function test() {

       echo "BaseClass::test() called\n";

   }

   

   final public function moreTesting() {

       echo "BaseClass::moreTesting() called\n";

   }

}



class ChildClass extends BaseClass {

   public function moreTesting() {

       echo "ChildClass::moreTesting() called\n";

   }

}

// Results in Fatal error: Cannot override final method BaseClass::moreTesting()

?>

Example 19-29. Final class example


<?php

final class BaseClass {

   public function test() {

       echo "BaseClass::test() called\n";

   }



   // Here it doesn't matter if you specify the function as final or not

   final public function moreTesting() {

       echo "BaseClass::moreTesting() called\n";

   }

}



class ChildClass extends BaseClass {

}

// Results in Fatal error: Class ChildClass may not inherit from final class (BaseClass)

?>