PHP雙冒號::的用法

雙冒號操做符即做用域限定操做符Scope Resolution Operator能夠訪問靜態、const和類中重寫的屬性與方法。

在類定義外使用的話，使用類名調用。在PHP 5.3.0，可使用變量代替類名。

Program List：用變量在類定義外部訪問

 
        01 
               
        02 
        <?php  
       
        03 
        class Fruit {  
       
        04 
            const CONST_VALUE = 'Fruit Color';  
       
        05 
        }  
       
        06 
           
        07 
        $classname = 'Fruit';  
       
        08 
        echo $classname::CONST_VALUE; // As of PHP 5.3.0  
       
        09 
           
        10 
        echo Fruit::CONST_VALUE;  
       
        11 
        ?>

Program List：在類定義外部使用::

 
        01 
             
        02 
        <?php  
       
        03 
        class Fruit {  
       
        04 
            const CONST_VALUE = 'Fruit Color';  
       
        05 
        }  
       
        06 
           
        07 
        class Apple extends Fruit  
       
        08 
        {  
       
        09 
            public static $color = 'Red';  
       
        10 
           
        11 
            public static function doubleColon() {  
       
        12 
                echo parent::CONST_VALUE . "\n";  
       
        13 
                echo self::$color . "\n";  
       
        14 
            }  
       
        15 
        }  
       
        16 
           
        17 
        Apple::doubleColon();  
       
        18 
        ?>

程序運行結果：

`1`	`Fruit Color Red`

Program List：調用parent方法

 
        01 
             
        02 
        <?php  
       
        03 
        class Fruit  
       
        04 
        {  
       
        05 
            protected function showColor() {  
       
        06 
                echo "Fruit::showColor()\n";  
       
        07 
            }  
       
        08 
        }  
       
        09 
           
        10 
        class Apple extends Fruit  
       
        11 
        {  
       
        12 
            // Override parent's definition  
       
        13 
            public function showColor()  
       
        14 
            {  
       
        15 
                // But still call the parent function  
       
        16 
                parent::showColor();  
       
        17 
                echo "Apple::showColor()\n";  
       
        18 
            }  
       
        19 
        }  
       
        20 
           
        21 
        $apple = new Apple();  
       
        22 
        $apple->showColor();  
       
        23 
        ?>

程序運行結果：

`1`	`Fruit::showColor()`

`2`	`Apple::showColor()`

Program List：使用做用域限定符

 
        01 
             
        02 
        <?php  
       
        03 
            class Apple  
       
        04 
            {  
       
        05 
                public function showColor()  
       
        06 
                {  
       
        07 
                    return $this->color;  
       
        08 
                }  
       
        09 
            }  
       
        10 
           
        11 
            class Banana  
       
        12 
            {  
       
        13 
                public $color;  
       
        14 
           
        15 
                public function __construct()  
       
        16 
                {  
       
        17 
                    $this->color = "Banana is yellow";  
       
        18 
                }  
       
        19 
           
        20 
                public function GetColor()  
       
        21 
                {  
       
        22 
                    return Apple::showColor();  
       
        23 
                }  
       
        24 
            }  
       
        25 
           
        26 
            $banana = new Banana;  
       
        27 
            echo $banana->GetColor();  
       
        28 
        ?>

程序運行結果：

`1`	`Banana is yellow`

Program List：調用基類的方法

 
        01 
               
        02 
        <?php  
       
        03 
           
        04 
        class Fruit  
       
        05 
        {  
       
        06 
            static function color()  
       
        07 
            {  
       
        08 
                return "color";  
       
        09 
            }  
       
        10 
           
        11 
            static function showColor()  
       
        12 
            {  
       
        13 
                echo "show " . self::color();  
       
        14 
            }  
       
        15 
        }  
       
        16 
           
        17 
        class Apple extends Fruit  
       
        18 
        {  
       
        19 
            static function color()  
       
        20 
            {  
       
        21 
                return "red";  
       
        22 
            }  
       
        23 
        }  
       
        24 
           
        25 
        Apple::showColor();  
       
        26 
        // output is "show color"!  
       
        27 
           
        28 
        ?>

程序運行結果：

`1`	`show color`