Let's talk about the basics of object-oriented programming in PHP (2)

This article mainly talks about the foundation of PHP object-oriented programming (2). It has certain learning value. Interested friends can learn about it.

In some small projects, you will frequently come into contact with the inheritance, encapsulation, polymorphism and other features of classes, and use the functions of the class itself.

But in large projects, class interfaces are often used for implementation, because interfaces do not involve the implementation of specific functions of the class, but interfaces will limit the functions of the class.

A complex and large-scale software needs to be composed of numerous functional classes. These functional classes need to be completed by multiple programmers. Among them, the software architect needs to specify the involved mode, team division of labor and other tasks.

This brings about the problem of programming unity. How to ensure that key functions can be well implemented requires a design interface that can take into account all aspects. Class interfaces are usually used, although PHP can use many method.

Features such as encapsulation, foundation, and polymorphism of classes all involve the functions of classes, which are generally implemented in small projects using class functions.

But in large-scale projects, the software needs to have many functions, which requires many functional classes, and these functional classes are usually completed by multiple programmers, so among the many programmers, The problem of unified programming arises. How to ensure that the functions of the software can be well realized?

This requires defining a set of functions in advance before software design, and then programmers implement these functions one by one.

There are many methods that can be used in PHP, usually implemented using class interfaces. A set of functions is defined in the interface, but the implementation of the functions requires programmers to implement them one by one, thus ensuring the integrity of the software functions.

1. Definition of interface

The interface is not a functional class, so specific function implementation methods cannot be defined in the interface class.

Use the interface keyword when defining an interface. The naming format is: I interface name.

Usually the members defined in the interface must be methods of the functional class and cannot be member attributes of the functional class.

A few points to note:

① Interface members must have global access permissions, so access modifiers cannot be added;

② Interface members cannot use constants, static methods, etc. Properties;

　　③Interface members cannot define constructors.

　④Interfaces can be inherited like classes. After inheritance, the sub-interface will get all the members of the parent interface.

2. Implementation of interface

Interfaces can only define functions, but cannot implement specific functions. If you want to realize the functions defined in the interface, you must use ordinary functional classes to implement them.

Format: implements interface name

Note: All member methods in the interface must be defined in the functional class, and no one can be left out.

The following is demonstrated through a simple example

In the interface file, define two interfaces Imyinterce, Imys (Imyinterface sub-interface)

<?php 
/**
*    定义接口Imyinterface
*/
interface Imyinterface{
    function add1();
    function add2($s);
    function add3($t=0);
}

//接口的继承
interface Imys extends Imyinterface{
    function del();
    function edit();
    function update($str);
    function select($id,$str);
}

?>

Then define a functional class to implement the interface. If you haven't figured out how to implement the function, you can implement it through an empty method. It cannot be omitted, otherwise an error will be reported, indicating that the functional class contains an abstract method, which must be implemented.

Only the update and select methods in the sub-interface Imy are implemented here. The other methods have not been implemented yet, and empty methods are used instead.

<?php 
require "./Imyinterface.interface.php";
class MyClass implements Imys{
    function add1(){
        //空方法，暂无具体实现方法，虽然功能类继承Imys，但是接口Imys又继承Imyinterface,因此Imyinterface里的方法也必须要实现
    }
    function add2($str){
        //同上
    }
    function add3($t=0){
        //同上
    }
    function del(){
        //空方法，暂无具体实现方法
    }
    function edit(){
        //空方法，暂无具体实现方法
    }
    function update($str="字符串"){
        return $str;
    }
    function select($id=0,$str="字符串"){
        return $id.$str;
    }

}
?>

Test code

<?php 
require "./MyClass.class.php";
header("Content-type:text/html;charset=utf-8");

$mys =new MyClass();
echo $mys->select();
?>

Browse effect

The above introduces the process of standardizing and unifying procedures in large-scale software design , usually using interfaces. However, the interface can only define the abstract functions of the program, but does not provide specific functions. Ordinary class members, such as constants, static properties and other ordinary members cannot be defined in the interface.

Abstract classes are designed for class inheritance. Ordinary class members can be defined in abstract classes. At this point, abstract classes are much more flexible than interfaces.

When defining an abstract class, you need to add the abstract keyword, and then define ordinary member methods in the abstract class. This ordinary method does not require specific function code.

Most MVC frameworks are built using PHP abstract classes. Abstract classes can be simply understood as a combination of ordinary classes and interfaces, that is, abstract=class interface.

Common points between interfaces and abstract classes:

① Neither interfaces nor abstract classes can be instantiated. Interfaces need to be implemented using the implements keyword, while abstract classes use the extends keyword of ordinary classes to inherit. .

　② Both interfaces and abstract classes contain method declarations that have not yet been implemented.

　③ Derived classes must implement unimplemented methods. Abstract classes are abstract methods, and interfaces are all members.

The difference between interfaces and abstract classes:

　①Abstract classes cannot be sealed, but interfaces can.

　②Concrete methods implemented by abstract classes are virtual by default, but class methods that implement interfaces are real by default.

　③The abstract class must list all members in the base class list of the class so that the implementation class can implement it, but the interface allows empty methods.

After understanding the concepts of interfaces and abstract classes, let’s take a closer look at the definition and implementation of abstract classes.

在PHP中，抽象类不能为空类或普通类，至少需要提供一个抽象方法，而抽象类和抽象方法都需要关键字abstract。

例如，定义一个简单的CURD抽象类(数据库的增删改查)

<?php 
/**
*    抽象类的定义
*/
abstract class BaseClass{
    //查询，抽象方法
    abstract function query($sql);
    //插入,抽象方法
    abstract function insert($sql);
    //更新,抽象方法
    abstract function update($sql);
    //删除,抽象方法
    abstract function delete($sql);

    //数据库连接,普通类方法
    protected $link;
    //sql语句
    protected $sql;
    //结果
    protected $arr;
    protected function Conn(){
        $this->link=mysql_connect("localhost","root","123") or die("数据库连接失败").mysql_error();
        if($this->link){
            mysql_select_db("db_match",$this->link) or die("数据库选择失败").mysql_error();
        }
        return $this->link;
    }
    //关闭数据库连接,普通类方法
    protected function CloseConn(){
        mysql_close($this->link);
    }
}
?>

抽象类的实现

<?php 
require "./BaseClass.class.php";    //引入抽象类
/**
*    实现抽象类
*/

class MyClass extends BaseClass {

    //实现抽象中的抽象方法，抽象类中抽象方法：query()、insert()、update()、delete()
    function query($sql){
        $this->Conn($this->link);
        $this->sql=$sql;
        $result=mysql_query($this->sql);
        while($row=mysql_fetch_assoc($result)){
            $this->arr=$row;
        }
        $this->CloseConn($this->link);    //关闭连接
        return print_r($this->arr);
    }

    function insert($sql){
        $this->Conn($this->link);
        $this->sql=$sql;
        mysql_query($this->sql,$this->link);
        $this->CloseConn($this->link);    //关闭连接
    }

    function update($sql){
        $this->Conn($this->link);
        $this->sql=$sql;
        mysql_query($this->sql,$this->link);
        $this->CloseConn($this->link);    //关闭连接
    }
    function delete($sql){
        $this->Conn($this->link);
        $this->sql=$sql;
        mysql_query($this->sql,$this->link);
        $this->CloseConn($this->link);    //关闭连接
    }
}
?>

测试代码

<?php 
require "./MyClass.class.php";
header("Content-type:text/html;charset=utf-8");

$mys =new MyClass();
$mys->query("select * from `match`");
//输出结果：Array ( [m_id] => 8 [t1_id] => 5 [t2_id] => 6 [t1_score] => 2 [t2_score] => 1 [m_time] => 1421571600 )
$mys->insert("insert into `match`(m_id,t1_id,t2_id,t1_score,t2_score,m_time) values(9,5,3,3,3,1451571600)");
//添加成功
$mys->update("update `match` set m_time =1111111111 where m_id=9");
//修改成功
$mys->delete("delete from `match` where m_id=9");
//删除成功
?>

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