php计算抽奖的概率

<?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;
}
$prize_arr = array(
'0' => array('id'=>1,'prize'=>'1000000514','v'=>2),
'1' => array('id'=>2,'prize'=>'1000000513','v'=>5),
'2' => array('id'=>3,'prize'=>'1000000512','v'=>13),
'3' => array('id'=>4,'prize'=>'1000000511','v'=>15),
'4' => array('id'=>5,'prize'=>'1000000510','v'=>25),
'5' => array('id'=>6,'prize'=>'1000000509','v'=>30),
'6' => array('id'=>7,'prize'=>'1000000508','v'=>10),
);
foreach ($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);

?>