Object-oriented PHP (3)

<code><span><span><?php</span>header(<span>"Content-Type: text/html; charset=utf-8"</span>);<span>//去除中文乱码</span><span>/**
*   1.parent关键字可以用于调用父类中被重写了的方法
*   2.self关键字可以用于访问类自身的成员方法、静态方法和类常量，自身属性不能被访问；使用常量的时候，常量名称不需要加$
*   3.static关键字用于访问类自身定义的静态成员，访问静态属性时需要在属性前加$
*/</span><span><span>class</span><span>BaseClass</span>{</span><span>public</span><span><span>function</span><span>test</span><span>()</span>{</span><span>echo</span><span>"BaseClass::test called.<br/>"</span>;
    }
    <span>public</span><span><span>function</span><span>test1</span><span>()</span>{</span><span>echo</span><span>"BaseClass::test1 called.<br/>"</span>;
    }
}
<span><span>class</span><span>ChildClass</span><span>extends</span><span>BaseClass</span>
    {</span><span>const</span> C>"类中定义的一个const常量"</span>;
        <span>private</span><span>static</span><span>$staticValue</span>=<span>"这是类的static常量"</span>;
        <span>public</span><span><span>function</span><span>test</span><span>(<span>$value</span>=null)</span>{</span><span>//没有默认值会报错</span><span>echo</span><span>"ChildClass::test called "</span>.<span>$value</span>.<span>"<br/>"</span>;
            <span>echo</span><span>parent</span>::test();<span>//调用被重写的父类方法</span><span>self</span>::called();
            <span>echo</span><span>self</span>::CONST_VALUE.<span>"<br/>"</span>;
            <span>echo</span><span>self</span>::<span>$staticValue</span>.<span>"<br/>"</span>;
        }
        <span>public</span><span><span>function</span><span>called</span><span>()</span>{</span><span>echo</span><span>"类的一个方法"</span>.<span>"<br/>"</span>;
        }
    }

<span>$obj</span>=<span>new</span> ChildClass();
<span>$obj</span>->test(<span>"'222'"</span>);
<span>//$obj->test1();</span><span>?></span></code>