What are the differences between static, self, and $this in PHP?

The differences between static, self, and $this in php are: 1. [$this] represents a reference to the object, written in a non-static method in the class; 2. Self is different from this, it points to the class itself , does not point to any instantiated object; 3. static is generally used to access static variables and static methods in a class.

The differences between static, self, and $this in php are:

1, $this Represents a reference to an object. $this is written in a non-static method in a class. When the class is instantiated, whoever calls the method (usually an object call) $this represents a reference to the object.

<?php
class Person {
    public $name;
    public function getName() {
        echo $this->name;
    }
}
$p = new Person();
$p2 = new Person();
$p->name = "小红";
$p2->name = "小明";
$p->getName();  // 小红
$p2->getName();  // 小明

2. self is different from this. It points to the class itself and does not point to any instantiated object. Generally used to access static variables and static methods in a class, and are also methods written in the class. Which class self is written in indicates the reference of the class

<?php
class Person {
    public static $name = "小红";
    public static function getName() {
        echo self::$name;
    }
}
$p = new Person();
$p2 = new Person();
$p::getName();  // 小红
$p2::getName();  // 小红
$p::$name = "小明";
$p::getName();  // 小明
$p2::getName();  // 小明

3, static Generally used to access static variables and static methods in a class, which are also methods written in the class. When the class calls the method, static means that class (binding that class)

<?php
class A {
    public function say() {
        echo "Hello";
    }
    public function saySelf() {
       //static 和 self 可以调用非静态方法  不能调用非静态属性  静态方法中不能有$this
      // static 和 self 可以写在非静态的方法中 ，可以使用对象调用
        self::say();
    }
    public function sayStatic() {
        static::say();
    }
}
class B extends A {
    public function say() {
        echo "World";
    }
}
$b = new B();
$b->say();  // World
$b->saySelf();  // Hello
$b->sayStatic();  // World

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