<?php
/**
 * $this调用本类或父类的非静态属性或方法，self调用本类的静态属性或方法，
 * parent用于调用父类的静态属性或方法
 */
class Exam{
    public $str="var1\n";
    public static $num=1;
    
    function __construct($var){
        return $this->str=$var;
    }
    
    /**
     * Enter description here...
     *
     * @return unknown
     */
    function myFunction(){
        return $this->str.="I'm Working\n";
    }
    
    /**
     * Enter description here...
     *
     * @return unknown
     */
    function __destruct(){
        print self::$num+=4;
        print "\n";
    }
}

class Exam2 extends Exam {
    public $var;
    function __construct($x){
        return $this->var=parent::$num+$x;
    }
}

$o1=new Exam("liushuimengchun!");
echo "\n";
echo $o1->myFunction();
echo "\n";
$o2=new Exam2(5);
echo "\n";
echo $o2->var;

/*
输出：
liushuimengchun!I'm Working


65
9
*/
?>