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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 #1 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 #2 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)
?>

Note: Properties cannot be declared final, only classes and methods may be declared as final.

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