抽奖概率算法

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<?php
function getRand($proArr) {   
    $result = [];
    foreach ($proArr as $key => $val) { 
        $arr[$key] = $val['v']; 
    } 
    // 概率数组的总概率  
    $proSum = array_sum($arr);        
    asort($arr);
    // 概率数组循环   
    foreach ($arr as $k => $v) {   
        $randNum = mt_rand(1, $proSum);   
        if ($randNum <= $v) {   
            $result = $proArr[$k];   
            break;   
        } else {   
            $proSum -= $v;   
        }         
    }     
    return $result;
}

$arr = [   
    ['id'=>1, 'name'=>'特等奖', 'v'=>1],
    ['id'=>2, 'name'=>'一等奖', 'v'=>5),
    ['id'=>3, 'name'=>'二等奖', 'v'=>10],
    ['id'=>4, 'name'=>'三等奖', 'v'=>12],
    ['id'=>5, 'name'=>'四等奖', 'v'=>22],
    ['id'=>6, 'name'=>'没中奖', 'v'=>50]
];  

$result = [];
for($i=0; $i<10000; $i++) {
    $rand = getRand($arr);
    isset($result[$rand['name']])? $result[$rand['name']]+=1: $result[$rand['name']] = 1;
}
asort($result);
var_dump($result);