The final keyword prevents child classes from overriding a method or constant by
prefixing the definition with final
. If the class
itself is being defined final then it cannot be extended.
Example #1 Final methods example
<?phpclass 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 #2 Final class example
<?phpfinal class BaseClass { public function test() { echo "BaseClass::test() called\n"; } // As the class is already final, the final keyword is redundant 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)?>
Example #3 Final constants example as of PHP 8.1.0
<?phpclass Foo{ final public const X = "foo";}class Bar extends Foo{ public const X = "bar";}// Fatal error: Bar::X cannot override final constant Foo::X?>
Note: Properties cannot be declared final: only classes, methods, and constants (as of PHP 8.1.0) may be declared as final. As of PHP 8.0.0, private methods may not be declared final except for the constructor.