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PHP : Language Reference : Classes and Objects (PHP 5) : Final Keyword

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 10.29. Final methods example

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<?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 10.30. Final class example

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<?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)
?>


Code Examples / Notes » language.oop5.final

liumr
this key word can describe a class or a class member function

penartur
Note that you cannot ovverride final methods even if they are defined as private in parent class.
Thus, the following example:
<?php
class parentClass {
   final private function someMethod() { }
}
class childClass extends parentClass {
   private function someMethod() { }
}
?>
dies with error "Fatal error: Cannot override final method parentClass::someMethod() in ***.php on line 7"
Such behaviour looks slight unexpected because in child class we cannot know, which private methods exists in a parent class and vice versa.
So, remember that if you defined a private static method, you cannot place method with the same name in child class.

slorenzo
<?php
class parentClass {
   public function someMethod() { }
}
class childClass extends parentClass {
   public final function someMethod() { } //override parent function
}
$class = new childClass;
$class->someMethod(); //call the override function in chield class
?>

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Final Keyword
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Late Static Bindings
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