<?php
class Counter
{
private static $count = 0;
const VERSION = 2.0;

function __construct()
{
self::$count++;
}

function __destruct()
{
self::$count--;
}

static function getCount()
{
return self::$count;
}
};

//创建一个实例,则__construct()将执行
$c = new Counter();

//输出 1
print(Counter::getCount() . "<br>n");

//输出类的版本属性
print("Version used: " . Counter::VERSION . "<br>n");
?>