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 19-29. 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 19-30. 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)
?>
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