The difference between inherited classes and implemented interfaces in PHP: 1. PHP inheritance belongs to single inheritance, which ensures unity, but is not flexible enough. Implementing interfaces is a supplement to single inheritance; 2. Implementing interfaces can be done in different places. Expand the functionality of a certain class without destroying the hierarchical relationship.
The operating environment of this tutorial: Windows 10 system, PHP version 7.1, DELL G3 computer
1. Comparison between inheritance and interface implementation:
(1) PHP inheritance belongs to single inheritance, which ensures unity, but is not flexible enough. Implementing interfaces is a supplement to single inheritance;
(2) Implementing interfaces can extend the functionality of a certain class without destroying the class hierarchical relationship.
<?php class Monkey { public $age; public $name; public function climbing() { echo "猴子会爬树<br/>"; } } interface iBirdable { public function fly(); } interface iFishable { public function swimming(); } class LittleMonkey extends Monkey implements iBirdable,iFishable { public function fly() { echo "猴子还会飞<br/>"; } public function swimming() { echo "猴子也会游泳<br/>"; } } $littleMonkey = new LittleMonkey(); $littleMonkey -> climbing(); $littleMonkey -> fly(); $littleMonkey -> swimming(); ?>
2. Final keyword:
1. If a class does not want to be inherited by other classes (from a security perspective), it can be modified with final;
2 . If you hope that a certain method cannot be overridden by subclasses (you do not want the method to be overloaded by subclass methods), you can also use final modification.
<?php class A{ final public function getRate($salary){ return $salary*0.08; } } class B extends A{ //不能去覆盖父类的getRate方法. /*public function getRate($sal){ return $sal*0.01; }*/ } $b=new B(); echo $b->getRate(100)."<br/>"; ?>
3. Final cannot modify member variables (properties).
3. const:
1. When an attribute does not want to be modified, you can consider using const to make it a constant. For example, pi cannot be tampered with.
2. Basic syntax:
const constant name = assign initial value;
If you do not assign an initial value, it cannot be tampered with later and it will not have a value.
3. Modifiers cannot be written on constants. They default to public but cannot be written out.
4. Constant names are generally named in all capital letters.
5. Calling syntax:
Used inside the class:
self::constant name or class name::constant name;
in External use of the class:
Interface name::constant;
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