PHP实现计算抽奖概率算法

<?php
 //计算抽奖的概率
 function get_rand($proArr) {
 $result = '';
 $proSum = array_sum($proArr);
 foreach ($proArr as $key => $proCur) {
  $randNum = mt_rand(1, $proSum);
  if ($randNum <= $proCur) {
  $result = $key;
  break;
  } else {
  $proSum -= $proCur;
  }
 }
 unset ($proArr);
 return $result;
 }
 $prize_arr = array(
 '0' => array('id'=>1,'prize'=>'家电','v'=>2),
 '1' => array('id'=>2,'prize'=>'数码相机','v'=>5),
 '2' => array('id'=>3,'prize'=>'iPad','v'=>13),
 '3' => array('id'=>4,'prize'=>'LED显示器','v'=>15),
 '4' => array('id'=>5,'prize'=>'U盘','v'=>25),
 '5' => array('id'=>6,'prize'=>'键盘','v'=>30),
 '6' => array('id'=>7,'prize'=>'鼠标垫','v'=>10),
 );
 foreach ($prize_arr as $key => $val) {
 $arr[$val['id']] = $val['v'];
 }
 $rid = get_rand($arr);
 $res['yes'] = $prize_arr[$rid-1]['prize'];
 unset($prize_arr[$rid-1]);
 shuffle($prize_arr);
 $prize_arrcount = count($prize_arr);
 for($i=0;$i<$prize_arrcount;$i++){
 $pr[] = $prize_arr[$i]['prize'];
 }
 $res['no'] = $pr;
 //抽奖结果
 $ro = $res['yes'];
 print_r($ro);
?>

iPad