1、=>的用法
在php中数组默认键名是整数,也可以自己定义任意字符键名(最好是有实际意义),如:

$css=array('style'=>'0',‘color’=>‘green‘);

则$css['style']=='0',$css['color']=='green'。

2、->的用法
->用来引用对象的成员(属性与方法);

<?php
   $arr=['a'=>123,'b'=>456];//数组初始化
   echo $arr['a'];//数组引用
   print_r($arr);//查看数组
   class A{
     public $a=123;
     public $b=456;
   }
   $obj=new A();
   echo $obj->a;//对象引用
   print_r($obj);//查看对象
?>

输出结果:

Array(
    [a] => 123
    [b] => 456)
Object(
    [a] => 123
    [b] => 456)

3、::的用法
双冒号操作符即作用域限定操作符Scope Resolution Operator可以访问静态、const和类中重写的属性与方法。
1)Program List:用变量在类定义外部访问

<?php 
 class Fruit { 
     const CONST_VALUE = 'Fruit Color'; 
 } 
 
 $classname = 'Fruit'; 
 echo $classname::CONST_VALUE; // As of PHP 5.3.0 
 echo Fruit::CONST_VALUE;
?>

2)Program List:在类定义外部使用::

<?php 
 class Fruit { 
     const CONST_VALUE = 'Fruit Color'; 
 } 
  
 class Apple extends Fruit 
 { 
     public static $color = 'Red';
     public static function doubleColon() {
         echo parent::CONST_VALUE . "\n";
         echo self::$color . "\n";
     }
 }
 
 Apple::doubleColon();
?>

(3)Program List:调用parent方法

<?php 
 class Fruit 
 {
     protected function showColor() { 
         echo "Fruit::showColor()\n"; 
     } 
 } 
 class Apple extends Fruit
 {
     // Override parent's definition
     public function showColor()
     {
         // But still call the parent function
         parent::showColor();
         echo "Apple::showColor()\n";
     }
 }

 $apple = new Apple();
 $apple->showColor();
?>

(4)Program List:使用作用域限定符

<?php 
     class Apple 
     { 
         public function showColor() 
         { 
             return $this->color; 
         } 
     }

     class Banana12     {
         public $color;

         public function __construct()
         {
             $this->color = "Banana is yellow";
         }

         public function GetColor()
         {
             return Apple::showColor();
         }
     }

     $banana = new Banana;
     echo $banana->GetColor();
 ?>

(5)Program List:调用基类的方法

 <?php 

 class Fruit 
 { 
     static function color() 
     { 
         return "color"; 
     }

     static function showColor()
     {
         echo "show " . self::color();
     }
 }

 class Apple extends Fruit
 {
     static function color()
     {
         return "red";
     }
 }

 Apple::showColor();
 // output is "show color"!

 ?>

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