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.' ';
}
}
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'.' ';
}
}
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
The code is as follows
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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
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 {
private static $name="static class_a";
const PI=3.14;
Public $value;
Public static function getName()
{
return self::$name;
}
//This way of writing is wrong, static methods cannot access non-static properties
Public static function getName2()
{
return self::$value;
}
Public function getPI()
{
return self::PI;
}
}
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';.
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