1.靜態(tài)方法和屬性（通過類而不是對象來訪問數(shù)據(jù)和功能）
2.抽象類和接口（設(shè)計(jì)，實(shí)現(xiàn)分離）
3.錯(cuò)誤處理（異常）
4.Final類和方法（限制繼承）
5.攔截器（自動(dòng)委托）
6.析構(gòu)方法（對象銷毀前的清理工作）
7.克隆對象（創(chuàng)建對象的副本）
8.把對象解析成字符串

PS，學(xué)會(huì)從內(nèi)存的角度看代碼。想象計(jì)算機(jī)的微觀世界。

靜態(tài)方法的小例子

<?php
class StaticExample{
  static public $aNum = 10;
  static public function sayHello(){
    print "hello";
  }
}
print StaticExample::$aNum."<br/>";
StaticExample::sayHello();

tips:

1.靜態(tài)方法不能訪問類中的普通屬性，因?yàn)槟切傩詫儆谝粋€(gè)對象，但可以訪問靜態(tài)屬性。
2.我們不能再對象中調(diào)用靜態(tài)方法，因此不能再靜態(tài)方法中使用偽變量$this。

靜態(tài)方法的大例子

<?php
class ShopProduct{
  private $title;
  private $producerMainName;
  private $producerFirstName;
  protected $price;
  private $discount = 0;
  private $id = 0;
  function __construct($title,$firstName,$mainName,$price){
    $this->title = $title;
    $this->producerFirstName = $firstName;
    $this->producerMainName = $mainName;
    $this->price = $price;
  }
  public function setID($id){
    $this->id = $id;
  }
  public static function getInstance($id,PDO $pdo){
    $query = "select * from products where id= '$id'";
    $stmt = $pdo->query($query);
    $row = $stmt->fetch();
    if(empty($row)){
      return null;
    }
    if($row['type'] == "book"){
      $product = new BookProduct($row['title'],
        $row['firstname'],
        $row['mainname'],
        $row['price'],
        $row['numpages']
        );
    }else if($row['type'] == "cd"){
      $product = new CdProduct($row['title'],
        $row['firstname'],
        $row['mainname'],
        $row['price'],
        $row['playLength']
        );
    }else{
      $product = new ShopProduct($row['title'],
        $row['firstname'],
        $row['mainname'],
        $row['price']
        );
    }
    $product->setId($row['id']);
    $product->setDiscount($row['discount']);
    return $product;
  }
  public function getProducerFirstName(){
    return $this->producerFirstName;
  }
  public function getProducerMainName(){
    return $this->producerMainName;
  }
  public function setDiscount($num){
    $this->discount = $num;
  }
  public function getDiscount(){
    return $this->discount;
  }
  public function getTitle(){
    return $this->title;
  }
  public function getPrice(){
    return ($this->price - $this->discount);
  }
  function getProducer(){
    return $this->producerFirstName." ".$this->producerMainName;
  }
  function getSummaryLine(){
    $base = "$this->title({$this->producerMainName},";
    $base .= "{$this->producerFirstName})";
    return $base;
  }
}
class CdProduct extends ShopProduct{
  private $playLength;
  function __construct($title,$firstName,$mainName,$price,$playLength){
    parent::__construct($title,$firstName,$mainName,$price);//繼承父類的構(gòu)造函數(shù)
    $this->playLength = $playLength;
  }
  function getPlayLength(){
    return $this->playLength;
  }
  function getSummaryLine(){
    $base = parent::getSummaryLine();
    $base .= ":playing time {$this->playLength}";
    return $base;
  }
}
class BookProduct extends ShopProduct{
  private $numPages = 0;
  function __construct($title,$firstName,$mainName,$price,$numPages){
    parent::__construct($title,$firstName,$mainName,$price);
    $this->numPages = $numPages;
  }
  function getnumPages(){
    return $this->numPages;
  }
  function getSummaryLine(){
    $base = parent::getSummaryLine();
    $base .= ":page count {$this->numPages}";
    return $base;
  }
}
$dsn = "sqlite:C:/Users/Administrator/Desktop/shop.db";
$pdo = new PDO($dsn,null,null);
$pdo->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);
$obj = ShopProduct::getInstance(1,$pdo);
echo $obj->getSummaryLine();

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希望本文所述對大家PHP程序設(shè)計(jì)有所幫助。

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