Sharing of static attributes and static method calls in PHP

Here we analyze the calling of static properties and static methods in PHP object-oriented. Regarding their calling (whether they can be called and how to call them), you need to understand where they are stored in the memory, so that it is very easy to understand. Static properties and methods (including static and non-static) have only one location in memory (rather than static properties, there are as many properties as there are instantiated objects).

Example:

<?php
header("content-type:text/html;charset=utf-8");
class Human{
 staticpublic $name = "小妹";
 public$height = 180;
 staticpublic functiontell(){
 echoself::$name;//静态方法调用静态属性，使用self关键词
 //echo $this->height;//错。静态方法不能调用非静态属性
//因为 $this代表实例化对象，而这里是类，不知道 $this 代表哪个对象
 }
 publicfunction say(){
 echoself::$name . "我说话了";
 //普通方法调用静态属性，同样使用self关键词
 echo$this->height;
 }
}
$p1 = new Human();
$p1->say();
$p1->tell();//对象可以访问静态方法
echo $p1::$name;//对象访问静态属性。不能这么访问$p1->name
//因为静态属性的内存位置不在对象里
Human::say();//错。say()方法有$this时出错；没有$this时能出结果
//但php5.4以上会提示
?>

(1). Static properties can be called without instantiation. Because the static attributes are stored in the class, the calling method is "class name::property name"; Conclusion:

(2) Static methods can be called without instantiation . Same as above
(3). Static methods cannot call non-static properties. Because non-static attributes need to be instantiated and stored in the object;
(4), static methods can call non-static methods, using the self keyword. In PHP, after a method is called self::, it is automatically converted into a static method;

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Detailed explanation of static static variables in PHP

Detailed explanation of the use of the static keyword in PHP

Detailed explanation of the usage and precautions of the static keyword in PHP

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