PHP implements lottery probability algorithm code

<?php
 //计算抽奖的概率
 function get_rand($proArr) {
 $result = &#39;&#39;;
 $proSum = array_sum($proArr);
 foreach ($proArr as $key => $proCur) {
  $randNum = mt_rand(1, $proSum);
  if ($randNum <= $proCur) {
  $result = $key;
  break;
  } else {
  $proSum -= $proCur;
  }
 }
 unset ($proArr);
 return $result;
 }
 $prize_arr = array(
 &#39;0&#39; => array(&#39;id&#39;=>1,&#39;prize&#39;=>&#39;家电&#39;,&#39;v&#39;=>2),
 &#39;1&#39; => array(&#39;id&#39;=>2,&#39;prize&#39;=>&#39;数码相机&#39;,&#39;v&#39;=>5),
 &#39;2&#39; => array(&#39;id&#39;=>3,&#39;prize&#39;=>&#39;iPad&#39;,&#39;v&#39;=>13),
 &#39;3&#39; => array(&#39;id&#39;=>4,&#39;prize&#39;=>&#39;LED显示器&#39;,&#39;v&#39;=>15),
 &#39;4&#39; => array(&#39;id&#39;=>5,&#39;prize&#39;=>&#39;U盘&#39;,&#39;v&#39;=>25),
 &#39;5&#39; => array(&#39;id&#39;=>6,&#39;prize&#39;=>&#39;键盘&#39;,&#39;v&#39;=>30),
 &#39;6&#39; => array(&#39;id&#39;=>7,&#39;prize&#39;=>&#39;鼠标垫&#39;,&#39;v&#39;=>10),
 );
 foreach ($prize_arr as $key => $val) {
 $arr[$val[&#39;id&#39;]] = $val[&#39;v&#39;];
 }
 $rid = get_rand($arr);
 $res[&#39;yes&#39;] = $prize_arr[$rid-1][&#39;prize&#39;];
 unset($prize_arr[$rid-1]);
 shuffle($prize_arr);
 $prize_arrcount = count($prize_arr);
 for($i=0;$i<$prize_arrcount;$i++){
 $pr[] = $prize_arr[$i][&#39;prize&#39;];
 }
 $res[&#39;no&#39;] = $pr;
 //抽奖结果
 $ro = $res[&#39;yes&#39;];
 print_r($ro);
?>

iPad