php抽奖概率计算类

<?php

/**
 * 概率计算类
 * 可用于抽奖等
 */
class Probability
{
    /**
     * 概率统计数据
     * thing => chance
     */
    var $data = array();
    var $chance_count = 0;

    function __construct($initdata = array()){
        if(!empty($initdata)){
            $this->data = $initdata;
            foreach($initdata as $d){
                $this->chance_count += $d['num'];
            }
        }
    }

    function addData($name, $chance){
        $this->data[]=array('name'=>$name, 'num'=>$chance);
        $this->chance_count += $chance;
    }

    function getOne(){
        $index = rand(0, $this->chance_count);
        foreach($this->data as $d){
            $index = $index-$d['num'];
            if($index<=0){
                return $d['name'];
            }
        }
        return '';
    }
}


/**
 * 使用示例
 */
$pro=new Probability();
$pro->addData('iphone',10);
$pro->addData('watch',30);
$pro->addData('$18',50);
$pro->addData('thank you',10);
$pro->addData('super big',1);
for($i=0;$i<100;$i++){
    echo $pro->getOne()."\n";
}