Winning probability algorithm (php can be used for scratch cards, big wheel and other lottery algorithms)

php winning probability algorithm, which can be used for scratch cards, big wheel and other lottery algorithms. Usage is very simple, there are detailed comments in the code, you can understand it at a glance

<?<span>php
</span><span>/*</span><span> * 经典的概率算法，
 * $proArr是一个预先设置的数组，
 * 假设数组为：array(100,200,300，400)，
 * 开始是从1,1000 这个概率范围内筛选第一个数是否在他的出现概率范围之内， 
 * 如果不在，则将概率空间，也就是k的值减去刚刚的那个数字的概率空间，
 * 在本例当中就是减去100，也就是说第二个数是在1，900这个范围内筛选的。
 * 这样 筛选到最终，总会有一个数满足要求。
 * 就相当于去一个箱子里摸东西，
 * 第一个不是，第二个不是，第三个还不是，那最后一个一定是。
 * 这个算法简单，而且效率非常 高，
 * 关键是这个算法已在我们以前的项目中有应用，尤其是大数据量的项目中效率非常棒。
 </span><span>*/</span><span>function</span> get_rand(<span>$proArr</span><span>) { 
    </span><span>$result</span> = ''<span>;  
    </span><span>//</span><span>概率数组的总概率精度 </span><span>$proSum</span> = <span>array_sum</span>(<span>$proArr</span><span>);  
    </span><span>//</span><span>概率数组循环 </span><span>foreach</span> (<span>$proArr</span><span>as</span><span>$key</span> => <span>$proCur</span><span>) { 
        </span><span>$randNum</span> = <span>mt_rand</span>(1, <span>$proSum</span><span>); 
        </span><span>if</span> (<span>$randNum</span> <= <span>$proCur</span><span>) { 
            </span><span>$result</span> = <span>$key</span><span>; 
            </span><span>break</span><span>; 
        } </span><span>else</span><span> { 
            </span><span>$proSum</span> -= <span>$proCur</span><span>; 
        }         
    } 
    </span><span>unset</span> (<span>$proArr</span><span>);  
    </span><span>return</span><span>$result</span><span>; 
} 


</span><span>/*</span><span> * 奖项数组
 * 是一个二维数组，记录了所有本次抽奖的奖项信息，
 * 其中id表示中奖等级，prize表示奖品，v表示中奖概率。
 * 注意其中的v必须为整数，你可以将对应的 奖项的v设置成0，即意味着该奖项抽中的几率是0，
 * 数组中v的总和（基数），基数越大越能体现概率的准确性。
 * 本例中v的总和为100，那么平板电脑对应的 中奖概率就是1%，
 * 如果v的总和是10000，那中奖概率就是万分之一了。
 * 
 </span><span>*/</span><span>$prize_arr</span> = <span>array</span><span>( 
    </span>'0' => <span>array</span>('id'=>1,'prize'=>'平板电脑','v'=>1), 
    '1' => <span>array</span>('id'=>2,'prize'=>'数码相机','v'=>5), 
    '2' => <span>array</span>('id'=>3,'prize'=>'音箱设备','v'=>10), 
    '3' => <span>array</span>('id'=>4,'prize'=>'4G优盘','v'=>12), 
    '4' => <span>array</span>('id'=>5,'prize'=>'10Q币','v'=>22), 
    '5' => <span>array</span>('id'=>6,'prize'=>'下次没准就能中哦','v'=>50),<span>
); 

</span><span>/*</span><span> * 每次前端页面的请求，PHP循环奖项设置数组，
 * 通过概率计算函数get_rand获取抽中的奖项id。
 * 将中奖奖品保存在数组$res['yes']中，
 * 而剩下的未中奖的信息保存在$res['no']中，
 * 最后输出json个数数据给前端页面。
 </span><span>*/</span><span>foreach</span> (<span>$prize_arr</span><span>as</span><span>$key</span> => <span>$val</span><span>) { 
    </span><span>$arr</span>[<span>$val</span>['id']] = <span>$val</span>['v'<span>]; 
} 
</span><span>$rid</span> = get_rand(<span>$arr</span>); <span>//</span><span>根据概率获取奖项id </span><span>$res</span>['yes'] = <span>$prize_arr</span>[<span>$rid</span>-1]['prize']; <span>//</span><span>中奖项 </span><span>unset</span>(<span>$prize_arr</span>[<span>$rid</span>-1]); <span>//</span><span>将中奖项从数组中剔除，剩下未中奖项 </span><span>shuffle</span>(<span>$prize_arr</span>); <span>//</span><span>打乱数组顺序 </span><span>for</span>(<span>$i</span>=0;<span>$i</span><<span>count</span>(<span>$prize_arr</span>);<span>$i</span>++<span>){ 
    </span><span>$pr</span>[] = <span>$prize_arr</span>[<span>$i</span>]['prize'<span>]; 
} 
</span><span>$res</span>['no'] = <span>$pr</span><span>; 
</span><span>print_r</span>(<span>$res</span>); 

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