Some knowledge points about PHP classes

1. Class definition

<?php
class Cart{
   var $items;
   function add_item($artnr,$num){
      $this->items[$artnr += $num;
   }
}

A class cannot be defined in multiple files, nor can the class definition be divided into multiple PHP blocks (it can be divided inside a function).

You cannot define a class named:

stdClass

__sleep

__wakeup

In fact don’t define a class starting with __.

2. Constructor

If the

class Cart {
    var $todays_date;
    var $name;
    var $owner;
    var $items = array("VCR", "TV");
    function Cart() {
        $this->todays_date = date("Y-m-d");
        $this->name = $GLOBALS['firstname'];
        /* etc. . . */
    }
}

class does not have a constructor, the base class constructor will be called.

Constructor parameters can be assigned default values

<?php
class Constructor_Cart extends Cart {
    function Constructor_Cart($item = "10", $num = 1) {
        $this->add_item ($item, $num);
    }
}

// 买些同样的无聊老货
$default_cart = new Constructor_Cart;
// 买些实在货...
$different_cart = new Constructor_Cart("20", 17);
?>

@new can suppress errors that occur in the constructor.
3. Usage of classes

$cart = new Cart;
$cart->add_item("10", 1);

class uses $this internally to represent itself.

4. Class related functions

__autoload — 尝试加载未定义的类
call_user_method_array — 调用一个用户方法，同时传递参数数组（已废弃）
call_user_method — 对特定对象调用用户方法（已废弃）
class_alias — 为一个类创建别名
class_exists — 检查类是否已定义
get_called_class — 后期静态绑定（"Late Static Binding"）类的名称
get_class_methods — 返回由类的方法名组成的数组
get_class_vars — 返回由类的默认属性组成的数组
get_class — 返回对象的类名
get_declared_classes — 返回由已定义类的名字所组成的数组
get_declared_interfaces — 返回一个数组包含所有已声明的接口
get_declared_traits — 返回所有已定义的 traits 的数组
get_object_vars — 返回由对象属性组成的关联数组
get_parent_class — 返回对象或类的父类名
interface_exists — 检查接口是否已被定义
is_a — 如果对象属于该类或该类是此对象的父类则返回 TRUE
is_subclass_of — 如果此对象是该类的子类，则返回 TRUE
method_exists — 检查类的方法是否存在
property_exists — 检查对象或类是否具有该属性
trait_exists — 检查指定的 trait 是否存在

5. Inheritance

<?php
class Named_Cart extends Cart {
    var $owner;

    function set_owner ($name) {
        $this->owner = $name;
    }
}
?>

PHP does not support multiple inheritance.
5. Static method

<?php
class A {
    function example() {
        echo "I am the original function A::example().<br />\n";
    }
}

class B extends A {
    function example() {
        echo "I am the redefined function B::example().<br />\n";
        A::example();
    }
}

// A 类没有对象，这将输出
//   I am the original function A::example().<br />
A::example();

// 建立一个 B 类的对象
$b = new B;

// 这将输出
//   I am the redefined function B::example().<br />
//   I am the original function A::example().<br />
$b->example();
?>

6. Base class reference parent

<?php
class A {
    function example() {
        echo "I am A::example() and provide basic functionality.<br />\n";
    }
}

class B extends A {
    function example() {
        echo "I am B::example() and provide additional functionality.<br />\n";
        parent::example();
    }
}

$b = new B;

// 这将调用 B::example()，而它会去调用 A::example()。
$b->example();
?>

7. Serialization

<?php
// classa.inc:
  class A {
      var $one = 1;

      function show_one() {
          echo $this->one;
      }
  }

// page1.php:
  include("classa.inc");

  $a = new A;
  $s = serialize($a);
  // 将 $s 存放在某处使 page2.php 能够找到
  $fp = fopen("store", "w");
  fwrite($fp, $s);
  fclose($fp);

// page2.php:
  // 为了正常解序列化需要这一行
  include("classa.inc");

  $s = implode("", @file("store"));
  $a = unserialize($s);

  // 现在可以用 $a 对象的 show_one() 函数了
  $a->show_one();
?>

8. Magic function __sleep __wakeup

Reference:

http://php.net/manual/zh/oop4. php

The above introduces some knowledge points of the PHP class, including aspects of the content. I hope it will be helpful to friends who are interested in PHP tutorials.