Final---used before classes, methods.
The final class---cannot be inherited.
The final method---cannot be overwritten.
The final class 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, we set the math class, which involves the mathematical calculation methods we have to do, these algorithms are not necessary to modify, and there is no need to be inherited, we set it to final type.
Copy Code code as follows:
?
Declare a final class math
Final class math{
public static $PI = 3.14;
Public Function __tostring () {
Return "This is the math class. ";
}
}
$math = new Math ();
Echo $math;
Declaring class Supermath inherits from the math class
Class Supermath extends Math {
}
Execution can be an error and the final class cannot be inherited.
?>
Program Run Results
Copy Code code as follows:
Fatal Error:class Supermath may isn't inherit from final Class (Math) in E:\PHPProjects\test.php on line 14
Final method cannot be overridden
If you do not want a method in a class to override the quilt class, we can set this method to be the final method, with only the final modifier before this method.
If this method overrides the quilt class, an error will occur.
Copy Code code as follows:
?
Declare a final class math
Class math{
public static $PI = 3.14;
Public Function __tostring () {
Return "This is the math class. ";
}
Public final function Max ($a, $b) {
Return $a > $b? $a: $b;
}
}
Declaring class Supermath inherits from the math class
Class Supermath extends Math {
Public final function Max ($a, $b) {}
}
Execution can fail and the final method cannot be overridden.
?>
Program Run Results
Copy Code code as follows:
Fatal Error:class Supermath may isn't inherit from final Class (Math) in E:\PHPProjects\test.php on line 16
