::, ->, self, $this operator in PHP_PHP tutorial-PHP Tutorial-php.cn

When accessing member variables or methods in a PHP class, if the referenced variable or method is declared as const (defining constant) or static (declaring static), then you must use the operator::, otherwise if it is referenced The variable or method is not declared as const or static, then the operator -> must be used.

In addition, if you access a const or static variable or method from within the class, you must use self-reference. On the contrary, if you access a non-const or static variable or method from within the class, you must use self-reference. $this.

$this instance

The code is as follows

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代码如下

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// this是指向当前对象的指针

class test_this{
private $content; //定义变量

function __construct($content){ //定义构造函数
$this->content= $content;
    }
    function __destruct(){}//定义析构函数

    function printContent(){//定义打印函数
        echo $this->content.'
';
    }
}

$test=new test_this('北京欢迎你！'); //实例化对象
$test->printContent();//北京欢迎你！

// this is a pointer to the current object

代码如下

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//parent是指向父类的指针

class test_parent{ //基类
public $name; //定义姓名父类成员需要定义为public，才能够在继承类中直接使用 this来调用。
function __construct($name){
$this->name=$name;
    }
}
class test_son extends test_parent{ //派生类继承test_parent
    public $gender;//定义性别
    public $age;    //定义年龄
    function __construct($gender,$age){ //继承类的构造函数
        parent::__construct('nostop');//使用parent调用父类的构造函数,来进行对父类的实例化
        $this->gender=$gender;
        $this->age=$age;
    }
    function __destruct(){}
    function print_info(){
        echo $this->name.'是个'.$this->gender.'，今年'.$this->age.'岁'.'
';
    }
}

$nostop=new test_son('女性','22');//实例化test_son对象
$nostop->print_info();//执行输出函数 nostop是个女性，今年23岁

class test_this{
private $content; //Define variables

Function __construct($content){ //Define constructor
$this->content= $content;
}
Function __destruct(){}//Define destructor

Function printContent(){//Define printing function
echo $this->content.'
';
}
} $test=new test_this('Welcome to Beijing!'); //Instantiated object
$test->printContent();//Welcome to Beijing! ::Usage

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//parent is a pointer to the parent class class test_parent{ //base class
Public $name; //Define name Parent class members need to be defined as public before they can be called directly using this in the inherited class.
Function __construct($name){
            $this->name=$name;
}
}
class test_son extends test_parent{ // Derived class inherits test_parent
Public $gender;//Define gender
Public $age; //Define age
Function __construct($gender,$age){ //Inherit the constructor of the class
parent::__construct('nostop');//Use parent to call the constructor of the parent class to instantiate the parent class
          $this->gender=$gender;
           $this->age=$age;
}
Function __destruct(){}
Function print_info(){
echo $this->name.'is a'.$this->gender.', this year'.$this->age.'years old'.'
';
}
} $nostop=new test_son('female','22');//Instantiate the test_son object
$nostop->print_info();//Execute the output function nostop is a female, 23 years old this year

Use the form self::$name. Note that the declaration format of the const attribute is const PI=3.14, not const $PI=3.14

private static $name="static class_a";

The code is as follows

代码如下

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class clss_a {

     private static $name="static class_a";

     const PI=3.14;
     public $value;

     public static function getName()
     {
        return self::$name;
     }
     //这种写法有误，静态方法不能访问非静态属性
     public static function getName2()
     {
         return self::$value;
     }
     public function getPI()
     {
       return self::PI;
     }


}

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class clss_a {

const PI=3.14;

Public $value;

}

Another point to note is that if a class method is static, the properties it accesses must also be static. When the internal method of a class accesses attributes that are not declared const or static, use the form $this->value ='class_a';. http://www.bkjia.com/PHPjc/628859.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/628859.htmlTechArticleWhen accessing member variables or methods in a PHP class, if the referenced variable or method is declared as const ( Define constant) or static (declare static), then you must use the operator:...

Related labels：

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