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PHP introductory tutorial: Analysis of object-oriented features (inheritance, polymorphism, interfaces, abstract classes, abstract methods, etc.)
PHP introductory tutorial: Analysis of object-oriented features (inheritance, polymorphism, interfaces, abstract classes, abstract methods, etc.)
Dec 22, 2016 am 11:52 AM
The examples in this article describe the object-oriented features of PHP. Share it with everyone for your reference, the details are as follows:
Demo1.php
<?php
header('Content-Type:text/html; charset=utf-8;');
//創(chuàng)建一個電腦類
class Computer {
//什么叫做類內(nèi)，就是創(chuàng)建類的花括號內(nèi)的范圍叫做類內(nèi)，其他地方則類外。
//public 是對字段的公有化，這個字段類外即可訪問，賦值和取值
public $_name = '聯(lián)想';
}
$computer = new Computer();
$computer -> _name = 'Dell';
echo $computer->_name;
?>
Demo2.php
<?php
header('Content-Type:text/html; charset=utf-8;');
class Computer {
//private 是私有化，即對字段進行封裝的操作，類外無法訪問，取值和賦值都不能操作
private $_name = '聯(lián)想';
}
$computer = new Computer();
echo $computer->_name;
?>
Demo3.php
<?php
header('Content-Type:text/html; charset=utf-8;');
class Computer {
private $_name = '聯(lián)想';
//這個時候我采用一個公共對外的方法來訪問私有字段
//因為私有字段只能在類內(nèi)訪問，而對外的公共方法是類內(nèi)的。
//更而公共方法又是公共的，所以類外又可訪問。
public function _run(){
//字段在類內(nèi)調(diào)用的時候必須是類 -> 字段，而$_name只是一個普通變量而已。
//字段在類外調(diào)用的方法是對象 -> 字段，而類內(nèi)就必須使用 Computer -> _name
//但是在本類中，可以使用一個關(guān)鍵字來代替字來代替 Computer ，那就是 $this
echo $this ->_name;
}
}
$computer = new Computer();
$computer -> _run();
?>
Demo4.php
<?php
header ( 'Content-Type:text/html; charset=utf-8;' );
class Computer {
private $name;
private $model;
private $cpu;
private $keyboard;
private $show;
private $zb;
//必須寫個對外的入口，才可以取到
public function getName() {
return $this->name;
}
//必須寫一個對內(nèi)的入口，對私有字段進行賦值
public function setName($name) {
//這里的 $name 只是一個變量而已，參數(shù)而已
//$this->name 才是類的字段
$this->name = $name;
}
}
$computer = new Computer ();
echo $computer->getName();
$computer->setName('Dell');
echo $computer->getName();
?>
Demo5.php
<?php
header ( 'Content-Type:text/html; charset=utf-8;' );
class Computer {
private $_name;
private $_model;
private $_cpu;
//當類外的對象直接調(diào)用私有字段時，會跟著去檢查是否有攔截器，
//如果直接對 $_name 進行賦值，那么__set 方法就會攔截住，就不會報錯了。
//采用攔截器進行賦值和取值
//賦值
private function __set($_key,$_value){
//采用$_key = '_name',那么 $_value = '聯(lián)想'；
//$this ->_name = '聯(lián)想';
$this ->$_key = $_value;
}
//取值
private function __get($_key){
return $this -> $_key;
//如果 $_key = '_name' 那么 $this -> _name;
//如果 $_key = '_cpu' 那么 $this -> _cpu;
//如果 $_key = '_model' 那么 $this -> _model;
}
}
$computer = new Computer ();
$computer->_name = '聯(lián)想';
$computer->_cpu = '四核';
$computer->_model = 'i7';
echo $computer->_name;
echo $computer->_cpu;
echo $computer->_model;
?>
Demo6.php
<?php
header ( 'Content-Type:text/html; charset=utf-8;' );
class Computer {
private $_name;
private $_model;
private $_cpu;
//__set 和 __get 方法私有了，還是可以執(zhí)行，是因為
//因為目前程序的指針已經(jīng)在類內(nèi)了。而類內(nèi)可以執(zhí)行封裝的方法
//類內(nèi)執(zhí)行私有方法，不會出現(xiàn)任何錯誤。
//它只需要間接的攔截就可以了。攔截是在內(nèi)類執(zhí)行的。
//說白了，__set() 和 __get() 是 PHP 內(nèi)置的方法，具有一定的特殊性
private function __set($_key, $_value) {
$this->$_key = $_value;
}
private function __get($_key) {
return $this->$_key;
}
}
$computer = new Computer ();
$computer->_name = '聯(lián)想';
$computer->_cpu = '四核';
$computer->_model = 'i7';
echo $computer->_name;
echo $computer->_cpu;
echo $computer->_model;
?>
Demo7.php
<?php
header ( 'Content-Type:text/html; charset=utf-8;' );
class Computer {
const NAME = 'DELL';
}
//常量的輸出方法 類::常量
echo Computer::NAME; //DELL
?>
Demo8.php
<?php
header ( 'Content-Type:text/html; charset=utf-8;' );
class Computer {
public $_count = 0;
public function _add(){
$this -> _count++; //$_count = $_count+1 $_count++
}
}
//做一個累計的效果
$computer1 = new Computer();
$computer1 ->_add();
$computer1 ->_add();
$computer1 ->_add();
echo $computer1 -> _count;
echo '<br />';
$computer2 = new Computer();
$computer2 ->_add();
$computer2 ->_add();
$computer2 ->_add();
echo $computer2 -> _count;
?>
Demo9.php
<?php
header ( 'Content-Type:text/html; charset=utf-8;' );
class Computer {
public static $_count = 0;
public function _add(){
//如果是靜態(tài)成員字段，那么就應該用 self 來調(diào)用，而不是 $this
self::$_count++;
}
}
//做一個累計的效果
$computer1 = new Computer();
$computer1 ->_add();
echo Computer::$_count;
$computer1 ->_add();
echo Computer::$_count;
$computer1 ->_add();
echo Computer::$_count;
echo '<br />';
$computer2 = new Computer();
$computer2 ->_add();
echo Computer::$_count;
$computer2 ->_add();
echo Computer::$_count;
$computer2 ->_add();
echo Computer::$_count;
?>
Demo10.php
<?php
header ( 'Content-Type:text/html; charset=utf-8;' );
class Computer {
public static $_count = 0;
public static function _add(){
self::$_count++;
}
}
Computer::_add();
Computer::_add();
Computer::_add();
echo Computer::$_count;
?>
Demo11.php
<?php
header ( 'Content-Type:text/html; charset=utf-8;' );
class Computer {
}
$computer = new Computer();
echo $computer instanceof Computer;
?>
Demo12.php
<?php
header ( 'Content-Type:text/html; charset=utf-8;' );
//這是父類，電腦類
class Computer {
public $_name = '聯(lián)想';
public function _run(){
echo '聯(lián)想在運行!';
}
}
//子類，筆記本電腦類
class NoteComputer extends Computer {
}
$noteComputer = new NoteComputer();
echo $noteComputer -> _name;
$noteComputer -> _run();
?>
Demo13.php
<?php
header ( 'Content-Type:text/html; charset=utf-8;' );
class Computer {
public $_name = '聯(lián)想';
public function _run(){
echo '聯(lián)想在運行!';
}
}
class NoteComputer extends Computer {
//我不需要父類的字段和方法，那么可以采用重寫的方法覆蓋掉父類的字段和方法
public $_name = 'Dell';
public function _run(){
echo 'Dell在運行!';
}
}
$noteComputer = new NoteComputer();
echo $noteComputer -> _name;
$noteComputer -> _run();
?>
Demo14.php
<?php
header ( 'Content-Type:text/html; charset=utf-8;' );
class Computer {
//私有化，但是無法被子類繼承，這個時候就應該用受保護的修飾符來封裝
protected $_name = '聯(lián)想';
protected function _run(){
return '聯(lián)想在運行!';
}
}
class NoteComputer extends Computer {
public function getTop() {
echo $this->_name;
echo $this->_run();
}
}
$noteComputer = new NoteComputer();
$noteComputer -> getTop();
?>
Demo15.php
<?php
header ( 'Content-Type:text/html; charset=utf-8;' );
class Computer {
public $_name = '聯(lián)想';
public function _run(){
return '聯(lián)想在運行!';
}
}
class NoteComputer extends Computer {
//我子類已經(jīng)覆蓋了父類的字段和方法，
//但是我又要調(diào)用父類的字段和方法，那怎么辦呢?
public $_name = 'Dell';
public function _run(){
echo 'Dell在運行!';
echo parent :: _run();
}
}
$noteComputer = new NoteComputer();
echo $noteComputer -> _name;
$noteComputer -> _run();
//DellDell在運行!聯(lián)想在運行!
?>
Demo16.php
<?php
header ( 'Content-Type:text/html; charset=utf-8;' );
//final 如果加在類前面，表示這個類不能被繼承
// final class Computer {
// }
class Computer {
//final 如果加在方法前面，表示不能夠重寫些方法
final public function _run(){
}
}
class NoteComputer extends Computer {
public function _run(){
}
}
$noteComputer = new NoteComputer();
?>
Demo17.php
<?php
header ( 'Content-Type:text/html; charset=utf-8;' );
//創(chuàng)建一個抽象類，只要在 class 前面加上 abstract 就是抽象類了
//抽象類不能夠被實例化，就是創(chuàng)建對象
//只在類里面有一個抽象方法，那么這個類必須是抽象類，類前面必須加上 abstract
abstract class Computer {
public $_name = '聯(lián)想';
//抽象類里創(chuàng)建一個抽象方法
//抽象方法不能夠?qū)崿F(xiàn)方法體的內(nèi)容
abstract public function _run();
//我在抽象類里能否創(chuàng)建一個普通方法
public function _run2(){
echo '我是父類的普通方法';
}
}
//類不能夠?qū)崿F(xiàn)多繼承，只支持單繼承。
//抽象類是給子類用來繼承的，實現(xiàn)一種規(guī)范和資源的共享
class NoteComputer extends Computer {
//抽象類的抽象方法，子類必須重寫，不然會報錯。
//抽象類里的普通方法不需要重寫，子類會直接繼承下來
public function _run(){
echo '我是子類的方法';
}
}
$noteComputer = new NoteComputer();
$noteComputer -> _run();
$noteComputer -> _run2();
echo $noteComputer -> _name;
?>
Demo18.php
<?php
/*
* 到底應該用抽象類還是接口呢
* 如果你要繼承多個接口的方法規(guī)范，那么就用接口好了。
* 如果你要共享一個方法體內(nèi)容，那么就用抽象類。
* */
header ( 'Content-Type:text/html; charset=utf-8;' );
//創(chuàng)建一個接口
//接口也不能被實例化
//接口是為了規(guī)范實現(xiàn)它的子類，以達到統(tǒng)一的目的。也可以共享數(shù)據(jù)
interface Computer {
//成員字段必須是變量
const NAME = '成員 ';
//接口里的所有方法都是抽象方法，不能夠?qū)懛椒w
//并且接口的抽象方法不需要寫 abstract
public function _run();
public function _run2();
}
interface Computer2 {
public function _run3();
}
//子類繼承接口的說法，叫做實現(xiàn)，接口可以多實現(xiàn)
class NoteComputer implements Computer,Computer2 {
public function _run() {
echo '我重寫了run';
}
public function _run3() {
echo '我重寫了run3';
}
public function _run2() {
echo '我重寫了run2';
}
}
$noteComputer = new NoteComputer();
$noteComputer -> _run();
$noteComputer -> _run2();
$noteComputer -> _run3();
echo NoteComputer::NAME;
//接口 :: 常量
//echo Computer::NAME;
?>
Demo19.php
<?php
header ( 'Content-Type:text/html; charset=utf-8;' );
//什么叫做多態(tài)，字面意思，多種形態(tài)
//一個動作由不同的人去執(zhí)行，而產(chǎn)生不同的效果或者效果，即為多態(tài)。
//一個人通過不同的狀態(tài)去執(zhí)行同一種動作，形成不同的效果，也可以稱作為多態(tài)。
//園丁 剪 修理花草
//理發(fā)師 剪 理發(fā)
//總裁 剪 裁員
//人 筆記本 運行 win7開機了
//人 臺式機 運行 xp開機了
//創(chuàng)建一個接口，來規(guī)范運行的方法
interface Computer {
public function version(); //這個方法表示采用什么電腦
public function work(); //這臺電腦是怎么運行的
}
//創(chuàng)建一個筆記本的類實現(xiàn)接口
class NoteComputer implements Computer {
public function version() {
echo '筆記本';
}
public function work() {
echo '可以便攜式運行 win7';
}
}
//創(chuàng)建一個臺式機的類實現(xiàn)接口
class DesktopComputer implements Computer {
public function version() {
echo '臺式機';
}
public function work() {
echo '在工作站運行 XP';
}
}
//創(chuàng)建一個用戶
class Person {
//創(chuàng)建一個方法來接受電腦(筆記本電腦，也可以是臺式電腦)
//怎么接受，將他們的對象傳進來就 OK 啦。
public function _run($type) {
echo '這個人的';
$type -> version();
$type ->work();
}
}
//多態(tài)的原理，就是類都寫好了，不要去修改它，只要在類外的調(diào)用參數(shù)的更改
//而最后的結(jié)果也會得到更改，那么這個就是多態(tài)。
//有一個接口，兩個類，一個是筆記本的類，一個是臺式機的類
//創(chuàng)建了筆記本
$noteComputer = new NoteComputer();
//創(chuàng)建臺式機
$desktopComputer = new DesktopComputer();
//創(chuàng)建一個人
$person = new Person();
//使用電腦
$person -> _run($noteComputer); //這種傳遞，叫做對象引用的傳遞
?>
I hope this article will be helpful to everyone in PHP programming.
For more PHP introductory tutorials on object-oriented feature analysis (inheritance, polymorphism, interfaces, abstract classes, abstract methods, etc.), please pay attention to the PHP Chinese website!
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