PHP object-oriented final class and final method

final---used before classes and methods.
Final class---cannot be inherited.
Final method---cannot be overridden.
Final classes cannot be inherited.
If we do not want a class to be inherited, we use final to modify the class. This class will not be inherited. For example, the Math class we set involves the mathematical calculation methods we want to do. These algorithms do not need to be modified or inherited. We set it to a final type.

<? 
//声明一个final类Math 
final class Math{ 
public static $pi = 3.14; 

public function __toString(){ 
return "这是Math类。"; 
} 
} 
$math = new Math(); 
echo $math; 

//声明类SuperMath 继承自 Math类 
class SuperMath extends Math { 
} 
//执行会出错，final类不能被继承。 

?>

Program running results

Fatal error: Class SuperMath may not inherit from final class (Math) in E:\PHPProjects\test.php on line 14

The final method cannot be overridden
If we do not want a method in the class to be overridden by a subclass, we can set this method as a final method. You need to add the final modifier before this method.

If this method is overridden by a subclass, an error will occur.

<? 
//声明一个final类Math 
class Math{ 
public static $pi = 3.14; 
public function __toString(){ 
return "这是Math类。"; 
} 
public final function max($a,$b){ 
return $a > $b ? $a : $b ; 
} 
} 
//声明类SuperMath 继承自 Math类 
class SuperMath extends Math { 
public final function max($a,$b){} 
} 
//执行会出错，final方法不能被重写。 

?>

Program running results

Fatal error: Class SuperMath may not inherit from final class (Math) in E:\PHPProjects\test.php on line 16

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