php-doc-en/language/oop5/final.xml

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<!-- $Revision: 1.5 $ -->
 <sect1 id="language.oop5.final">
  <title>Final Keyword</title>
  <para>
   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.
  </para>
  
  <example>
   <title>Final methods example</title>
    <programlisting role="php">
<![CDATA[
<?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()
?> 
]]>
   </programlisting>
  </example>

  <example>
   <title>Final class example</title>
    <programlisting role="php">
<![CDATA[
<?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)
?> 
]]>
   </programlisting>
  </example>
 </sect1>
 
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