php入门2 单例模式

<span><span><?php</span><span><span>class</span><span>myclass</span>{</span><span>public</span><span>static</span><span>$mydata1</span>=<span>NULL</span>;
    <span>private</span><span><span>function</span><span>__construct</span><span>()</span>{</span><span>echo</span><span>"构造函数<br>"</span>;
    }
    <span>public</span><span>static</span><span><span>function</span><span>getinstall</span><span>()</span> {</span><span>if</span> (   <span>self</span>::<span>$mydata1</span>==<span>null</span>)
            {
                 <span>echo</span><span>"创建对象<br>"</span>;
                  <span>self</span>::<span>$mydata1</span> = <span>new</span>  myclass();
            }
            <span>return</span><span>self</span>::<span>$mydata1</span>;
    } 
    <span>public</span><span><span>function</span><span>test</span><span>()</span>
    {</span><span>echo</span><span>"hello2<br>"</span>;
    }

} 
<span>$f</span> = myclass::getinstall();
<span>$f</span>->test();

<span>$f2</span> = myclass::getinstall();
<span>$f2</span>->test();
<span>?></span></span>