<?php

function getPrize($prizes) {
    //概率数组的总概率精度
    $pro_sum = array_sum(array_column($prizes,'odds'));
    //概率数组循环
    foreach ($prizes as $item) {
        $rand_num = mt_rand(1, $pro_sum);
        if ($rand_num <= $item['odds']) {
            return $item;
        } else {
            $pro_sum -= $item['odds'];
        }
    }
    unset ($prizes);
}

$prize = [
    [
        'id'=>1,
        'prize_name'=>'奖品1',
        'val'=>1,
        'odds'=>68688
    ],
    [
        'id'=>2,
        'prize_name'=>'奖品2',
        'val'=>1,
        'odds'=>24500
    ],
    [
        'id'=>3,
        'prize_name'=>'奖品3',
        'val'=>1,
        'odds'=>5000
    ],
    [
        'id'=>4,
        'prize_name'=>'奖品4',
        'val'=>1,
        'odds'=>900
    ],
    [
        'id'=>5,
        'prize_name'=>'奖品5',
        'val'=>1,
        'odds'=>500
    ],
    [
        'id'=>6,
        'prize_name'=>'奖品6',
        'val'=>1,
        'odds'=>260
    ],
    [
        'id'=>6,
        'prize_name'=>'奖品7',
        'val'=>1,
        'odds'=>150
    ],
    [
        'id'=>6,
        'prize_name'=>'奖品8',
        'val'=>1,
        'odds'=>2
    ],
];

echo json_encode(getPrize($prize));