Final Keyword in PHP class

PHP 5 introduces the final keyword. It 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.

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 {
// Results in Fatal error: Cannot override final method BaseClass::moreTesting()
public function moreTesting() {
echo “ChildClass::moreTesting() called\n”;
}
}

OUTPUT :
Fatal error: Cannot override final method BaseClass::moreTesting() on line 15

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”;
}
}

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

OUTPUT :
Fatal error: Class ChildClass may not inherit from final class (BaseClass) on line 14