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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

<?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

<?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)
?>