单例模式PHP

单例模式例程：

<?php
class test{
  private  static  $_instance;
  private   function __construct($st)
    {
        $test_func=$st;
        $this->$test_func();
    }
    private  function  __clone(){}

    public static  function getInstance($st)
    {  if(!self::$_instance instanceof self)
        {
            self::$_instance=new self($st);
        }
        return self::$_instance;
    }

    function name()
    {
        echo 'name namenamenamename11111111 ';
    }

    function pass()
    {
        echo 'passpasspasspasspasspass22222222222 ';
    }

}
echo '12222222111<br/>';
$st=$_GET['st'];
test::getInstance($st);