Static variables and static methods for PHP

Static variables are also called class variables, and static methods are also called class methods.

Simply put, a static variable is a variable that all objects share. Static variables are also called class variables, and static methods are also called class methods.

How to define a static variable

Access modifier static variable name;

How to access static variables:

(1) outside the class: class Name:: $ class variable name

(2) inside the class:self::$ class variable name or:: $ class variable name

A group of children are playing games and new children are added to the game. Q: How to know how many children are playing games now, using object-oriented thinking.

The difference between a static variable and a workaround variable:

(1) Coupled with static is called statically variable or class variable, otherwise called instance variable;

(2) class variables are related to the class, the public properties;

(3) The instance variable belongs to the individual attribute of each object;

(4) class variables can be accessed directly by the class name:: Class variable name.

Mode one: Using global variables

What is a global variable? A variable that can be used anywhere in the program, called a global variable.

<?php
Global variables to play the number of games
Global $global _nums;
$global _nums=0;
Class child{
  Public $name;
  function __construct ($name) {
	$this->name= $name;
  }
  Public Function Join_game () {
  Declaration uses global variables
  Global $global _nums;
  $global _nums+=1;
  echo $this->name. ' Join the game. ' <br/> ";
  }
Create three children
}
$child 1=new Child ("www.bianceng.cn");
$child 1->join_game ();
$child 2=new Child ("Dick");
$child 2->join_game ();
$child 3=new Child ("King II");
$child 3->join_game ();
See how many people play games
echo "<br/> has". $global _nums. " People play games ";
?>

Mode two: Using static variables

<?php
Class child{
  Public $name;
  public static $nums = 0; Defining static variables
  function __construct ($name) {
	$this->name= $name;
  }
  Public Function Join_game () {
  Self:: $nums +=1;
  echo $this->name. ' Join the game. ' <br/> ";
  }
Create three children
}
$child 1=new Child ("www.bianceng.cn");
$child 1->join_game ();
$child 2=new Child ("Dick");
$child 2->join_game ();
$child 3=new Child ("King II");
$child 3->join_game ();
See how many people play games
echo "<br/> has". Child:: $nums. " People play games ";
?>

PHP static method

Static methods are also called class methods, and static methods belong to all object instances in the form of the following:

Access modifier static method name () {

  Statement

  }

When we manipulate static variables, we can consider using static methods

Note: Non-static properties (variables) cannot be accessed in class methods, and normal methods can access either static variables or non-static variables.

Use of class methods:

Outside the class:

Class Name:: Class method Name or object name-> class method name;

Inside the class:

Self:: Class method Name or class Name: Class method Name

Example: The sum of the statistics of tuition

<?php
  Class student{
     public static $fee = 0;
     Public $name;
     Constructors
     function __construct ($name) {
       $this->name= $name;
     }
     Entrance
     public static function Enterschool ($ifee) {
        Self:: $fee + = $ifee;
     }
     Get the total tuition fee
     public static function Getfee () {
        Return self:: $fee;
     }
  }
  Create a student
  $stu 1=new Student ("John");
  To invoke a static method by using the class name
  Student::enterschool (340); Equivalent to $stu1->enterschool (340);
  $stu 2=new Student ("Dick");
  $stu 2->enterschool (600);
   echo "Total tuition fee is:". Student::getfee ();
?>