php面向对象关键字

1. const 修饰类属性

    1 class Person
    2 {
    3     const HOST = 'localhost';
    4 
    5     public function say(){
    6         echo 'hello';
    7     }
    8 }
    9 
   10 echo Person::HOST;

2. final 最终版本，不允许被继承：修饰类或方法

   1 final class Person
   2 {
   3     const HOST = 'localhost';
   4 
   5     public function say(){
   6         echo 'hello';
   7     }
   8 }

   1 class Person
   2 {
   3     const HOST = 'localhost';
   4 
   5     final public function say(){
   6         echo 'hello';
   7     }
   8 }
3. static  修饰属性或方法

    1 class Person
    2 {
    3     public $name;
    4     static public $num;
    5 
    6     public function __construct($n){
    7         $this->name = $n;
    8         Person::$num++;
    9     }
   10 }
   11 new Person('user1');
   12 new Person('user2');
   13 new Person('user3');
   14 
   15 echo Person::$num; # 3

    1 # 类名可以直接调用不包含$this的方法，否则必须通过new类名调用
    2 
    3 class Person
    4 {
    5     public $name;
    6 
    7     public function __construct($n){
    8         $this->name = $n;
    9     }
   10 
   11     public function say(){
   12         echo "<p>my name is {$this->name}</p>";
   13     }
   14 
   15     static public function sum($i,$j){
   16         return $i+$j;
   17     }
   18 }
   19 
   20 echo Person::sum(5,25);