PHP object-oriented static methods, properties and constants

This article mainly introduces the static methods, properties and constants about PHP object-oriented, which has a certain reference value. Now I share it with you. Friends in need can refer to it

Static methods , attribute

Definition

Use the static keyword definition;

Declare the class attribute or method as static, that is, you cannot Instantiate, access directly.

Note:

1) Static properties cannot be accessed through instantiated objects;

2) Static methods can be accessed;

3) Static methods , cannot use $this

Usage method

 ：： 或  self::

The details are as follows:

  访问位置           调用属性           调用方法

类的内部/外部       类名：：属性名      类名：：方法名

   内部           self：：属性名      self/类名：：方法名

Comprehensive example

<?php

class MyClass
{
    // 静态属性
    public static $a = &#39;static&#39;;

    // 静态方法
    public static function func1()
    {
        echo &#39;静态方法&#39;;

        // 类的内部调用静态属性
        echo MyClass::$a;
        echo self::$a;

        // 类的内部调用静态方法
        MyClass::func2();
        self::func2();
    }

    // 试验静态方法调用另一个静态方法
    public static function func2()
    {
        echo &#39;This is static function 2.&#39;;
    }
}

// 类的外部调用静态属性、方法
echo MyClass::$a;
MyClass::func1();

// 实例化后再调用
$me = new MyClass();

echo $me::$a;   // 调用成功
// echo $me ->a;   调用失败
$me -> func1();  // 调用成功

Constant

constYou can define values ​​that remain unchanged in a class as constants.

The value of a constant must be a fixed value.

Call method, same as static.

Example

class MyClass
{
    public static $a = 'abc';
    const NUM = 123;
}

echo MyClass::$a;
echo &#39;<br/>&#39;;
echo MyClass::NUM;
echo &#39;<br/>&#39;;

// 修改静态属性
MyClass::$a = &#39;def&#39;;
echo MyClass::$a;
echo &#39;<br/>&#39;;

// 修改常量
//MyClass::NUM = 234;  赋值失败

Related recommendations:

php object-oriented constructor and destructor

php object-oriented encapsulation

php object-oriented classes and instantiated objects

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