相对于数字的概率

Question

I would like to make a roulette for my PHP site, so I need to set the probability of the items. So I created an array with the probability of the different items:

(the higher the number the higher the chance)

$porpList = [
0 => [
    "prop" => 10000,
    "css" => "gray"
],
1 => [
    "prop" => 1000,
    "css" => "green"
],
2 => [
    "prop" => 100,
    "css" => "blue"
],
3 => [
    "prop" => 10,
    "css" => "violet"
],
4 => [
    "prop" => 1,
    "css" => "yellow"
],
5 => [
    "prop" => 0.1,
    "css" => "orange"
]];

Now comes the difficult part: The User with a higher Level should have a greater chance to get better Items and a lower chance to get trash Items, so with level 1 the probability would be:

10000
1000
100
10
1
0.1

And with Level 50 the probability should be something like this:

1
1
10000
1000
100
10

Logically, I could create a table in which all the possibilities for each level are listed, but I would like to solve this with a formula or similar.

Does anyone know a way to do this?

Answer 1

If you want to implement an actual algorithm to determine probability. I'm out.

If you want to heighten the chances of people rolling better stuff, you could use code similar to this;

$rarities = [
    [
        'prop'  => 100000,
        'css'   => 'gray'
    ],
    [
        'prop'  => 10000,
        'css'   => 'green'
    ],
    [
        'prop'  => 1000,
        'css'   => 'blue'
    ],
    [
        'prop'  => 100,
        'css'   => 'violet'
    ],
    [
        'prop'  => 10,
        'css'   => 'yellow'
    ],
    [
        'prop'  => 1,
        'css'   => 'orange'
    ]
];
$level = 50;
$maxProp = (100000/$level);
$won = 'gray';
for ($i=0;$i<20;$i++)
{
    $roll = random_int(0, $maxProp);
    foreach ($rarities as $rarity)
    {
        if ($rarity['prop'] < $roll)
        {
            break;
        }
        $won = $rarity['css'];
    }
    echo '<span style="color: '.$won.'; font-weight: bold; font-familiy: Arial;">'.$roll.'</span><br/>';

The higher the level, the higher chances are something good will 'drop'.