学步园

php的继承功能还很不完善，并且很容易出错。运行下面的代码，看看结果是否是你所要的。

<?php<br /> interface IA<br /> {<br /> public function Print1();<br /> public function Print2();<br /> //private function Pritn3(); //error<br /> //public $m_var1; //error<br /> };<br /> abstract class CB<br /> {<br /> public abstract function Echo1();<br /> //private abstract function Echo2(); //error</p> <p> public function Echo3()<br /> {<br /> echo "CB::Echo3<br>";<br /> echo "m_var1 = " . $this->m_var1 . "<br>";<br /> echo "m_var2 = " . $this->m_var2 . "<br>";<br /> echo "m_var3 = " . $this->m_var3 . "<br>";<br /> echo "m_var4 = " . $this->m_var4 . "<br>";<br /> echo "m_var = " . CB::m_var . "<br>";<br /> echo "static m_var3 = " . CB::$m_var3 . "<br>";</p> <p> }<br /> public $m_var1;<br /> private $m_var2;<br /> public static $m_var3 = 11;<br /> protected $m_var4;<br /> const m_var = 10; //声明为常量<br /> };<br /> class CC implements IA<br /> {<br /> public function CC()<br /> {<br /> echo "constructor of CC has been called!<br>";<br /> }<br /> public function __destructor()<br /> {<br /> echo "destructor of CC has been called!<br>";<br /> }<br /> function Print1()<br /> {<br /> echo "CC::Print1()<br>";<br /> }<br /> function Print2()<br /> {<br /> echo "CC::Print2()<br>";<br /> }<br /> };<br /> class CD extends CB<br /> {<br /> public function CD()<br /> {<br /> echo "constructor of CD has been called!<br>";<br /> //parent::$m_var1 = 1; //error<br /> $this->m_var1 = 1;<br /> $this->m_var2 = 2; //因为父类中位private所以，无法直接去访问。因此，隐式的定义了一个变量<br /> $this->m_var3 = 3;<br /> $this->m_var4 = 4;<br /> $this->m_var = 5;<br /> }<br /> function Echo1()<br /> {<br /> echo "CD::Echo1()<br>";<br /> }<br /> };<br /> ?><br /> <?php<br /> //$objA = new IA;<br /> //$objB = new CB;<br /> $objC = new CC;<br /> $objD = new CD;<br /> $objC->Print1();<br /> $objC->Print2();<br /> $objD->Echo1();<br /> $objD->Echo3();<br /> ?> 

结果：

constructor of CC has been called!
constructor of CD has been called!
CC::Print1()
CC::Print2()
CD::Echo1()
CB::Echo3
m_var1 = 1
m_var2 = 
m_var3 = 3
m_var4 = 4
m_var = 10
static m_var3 = 11