PHP object-oriented programming method example analysis

<?php
class classname{
  var $attr1;
  var $attr2;
  public $attribute;
  const PI = 3.14;
  // 构造函数
  function __construct($param = &#39;default&#39;){
    echo "Constructor called with parameter $param<br />";
  }
  // 析构函数
  function __destruct(){
    echo &#39;<br />destruct&#39;;
  }
  //
  function oper1(){
    echo &#39;oper1<br />&#39;;
  }
  function oper2($param){
    $this->attr1 = $param;
    echo $this->attr1;
  }
  protected function oper3(){
    echo &#39;this is protected function<br />&#39;;
  }
  // 禁止继承
  final function oper5(){
  }
  function __get($name){
    return $this->$name;
  }
  function __set($name, $value){
    $this->$name = $value;
  }
  // 静态方法
  static function double($param){
    return $param * $param;
  }
}
$a = new classname(&#39;First&#39;);
$b = new classname(&#39;Second&#39;);
$c = new classname();
$c->oper2("hello");
echo &#39;<br />&#39;;
echo $c->attr1;
echo &#39;<br /><br />&#39;;
echo &#39; Per-Class常量 classname::PI -&#39;.classname::PI;
echo &#39;<br />静态方法: classname::double(3) - &#39; . classname::double(3);
echo &#39;<br />&#39;;
// 实现继承
echo &#39;实现继承<br />&#39;;
class B extends classname{
  function oper4(){
    $this->oper3(); // protected方法只能在
  }
  function oper1(){ // 重载
    echo &#39;this is class B /&#39;s oper1. <br />&#39;;
  }
}
$d = new B("forth");
$d->oper1();
$d->oper4();
// 接口
interface Displayable
{
  function display();
  function show();
}
class C implements Displayable
{
  function display(){
    echo &#39;这是对应接口的方法.<br />&#39;;
  }
  function show(){}
}
$e = new C();
$e->display();
echo &#39;检查$e是否为C的实例:&#39;;
echo ($e instanceof C) ? &#39;Yes&#39;:&#39;No&#39;;
// 克隆对象
$f = clone $e;
echo &#39;<br /><br />可以使用__clone()方法，在使用clone关键字时调用&#39;;
// 抽象类
abstract class E{}
// $f = new E(); // 这行将报错,不能实例化抽象类
//　参数重载，多态
class F{
  public $a = 1;
  public $b = 2;
  public $c = 3;
  function displayString($elem){
    echo &#39;<br />string:&#39;.$elem;
  }
  function displayInt($elem){
    echo &#39;<br />int:&#39;.$elem;
  }
  // 注意参数$p，是作为数组传入，必须使用下标访问
  function __call($method, $p){
    if ($method == &#39;display&#39;){
      if (is_string($p[0])){
        $this->displayString($p[0]);
      } else {
        $this->displayInt($p[0]);
      }
    }
  }
}
$g = new F();
$g->display(&#39;abc&#39;);
// 迭代器,读出实例的所有属性
foreach ($g as $att){
  echo &#39;<br />&#39;.$att;
}
// 反射
echo &#39;<br />&#39;;
$class = new ReflectionClass(&#39;F&#39;);
echo &#39;<pre class="brush:php;toolbar:false">&#39;;
echo $class;
echo &#39;